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1 EVOLVING CONCEPTS IN THE MANAGEMENT OF CHRONIC MYELOID LEUKEMIA. RECOMMENDATIONS FROM AN EXPERT PANEL ON BEHALF OF THE EUROPEAN LEUKEMIANET. Running title: Management of Chronic Myeloid Leukemia. Michele Baccarani1, Giuseppe Saglio2, John Goldman3, Andreas Hochhaus4, Bengt Simonsson5, FrederickAppelbaum6, Jane Apperley7, Francisco Cervantes8, Jorge Cortes9, Michael Deininger10, Alois Gratwohl11, François Guilhot12, Mary Horowitz13, Timothy Hughes14, Hagop Kantarjian9, Richard Larson15, Dietger Niederwieser16, Richard Silver17, Rudiger Hehlmann4 Authors institutional affiliations 1. M. Baccarani: Department of Hematology/Oncology “L. and A. Seràgnoli”, University of Bologna, Bologna, Italy 2. G. Saglio: Universityof Turinat Orbassano, Turin, Italy 3. J. Goldman: Hematology Branch, National Heart, Lung & Blood Institute, NIH, Bethesda, MD, USA 4. A. Hochhaus, R. Hehlmann: Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany 5. B. Simonsson: Department of Hematology, UniversityHospital, Uppsala, Sweden 6. F. Appelbaum: FredHutchinsonCancerResearchCenter, Seattle, WA, USA 7. J. Apperley: Department of Hematology, HammersmithHospital, London, UK 8. F. Cervantes: Hematology Department, Hospital Clinic, IDIBAPS, Universityof Barcelona, Barcelona, Spain 9. J. Cortes, H. Kantarjian: MD AndersonCancerCenter, Houston, TX, USA 10. M. Deininger: Oregon Health & Science University Cancer Institute, Portland, OR, USA 11. A. Gratwohl: Hematology, UniversityHospital, Basel, Switzerland 12. F. Guilhot: Oncology, Hematology and Cell Therapy, Medical Oncology, EA 3805 and Clinical Research Centre, CHULa Miletrie,Poitiers, France 13. M. Horowitz: Centre for International Blood and Marrow Transplant Research, MedicalCollege of Wisconsin, Milwaukee, IL, USA 14. T. Hughes: Instituteof Medicaland Veterinary Science, Adelaide, Australia 15. R. Larson: Universityof Chicago, Chicago, IL, USA 16. D. Niederwieser: Department of Hematology and Oncology, Universityof Leipzig, Leipzig, Germany Blood First Edition Paper, prepublished online May 18, 2006; DOI 10.1182/blood-2006-02-005686 Copyright © 2006 American Society of Hematology 2 17. R. Silver: New York Presbyterian-Weill Cornell Medical Center, New York, NY, USA Work supported by the EU, Sixth Framework Programme, Contract No. LSHC-CT-2004-503216 (European LeukemiaNet) Word count: Abstract 206 Manuscript 5414 Acknowledgement: The scientific contributions of Professor Jörg Hasford and of many members of the European LeukemiaNet, Work Package 4, are acknowledged. The scientific and the technical assistance of Simona Soverini, PhD, Alessandra Dorigo, PhD, Chiara Ferri, and Katia Vecchi is also kindly acknowledged. Correspondence: Michele Baccarani, MD Department of Hematology-Oncology “L. and A. Seràgnoli” S.Orsola-MalpighiHospital Via Massarenti 9 40138 Bologna– Italy Tel: xx39 051 390413 Fax xx39 051 398973 e-mail: [email protected] 3 ABSTRACT The introduction of imatinib mesylate (IM) has revolutionized the treatment of chronic myeloid leukemia (CML). Although experience is too limited to permit evidence-based evaluation of survival, the available data fully justify critical reassessment of CML management. The panel therefore reviewed treatment of CML since 1998. It confirmed the value of IM (400 mg/day) and of conventional allogeneic hematopoietic stem cell transplantation (alloHSCT). It recommended that the preferred initial treatment for most patients newly diagnosed in chronic phase should now be IM 400 mg daily. A dose increase of IM, or alloHSCT, or investigational treatments were recommended in case of failure and could be considered in case of suboptimal response. Failure was defined at 3 months (no hematologic response (HR)), 6 months (incomplete HR or no cytogenetic response (CgR)), 12 months (less than partial CgR (Ph+ >35%)), 18 months (less than complete CgR), and in case of HR or CgR loss, or appearance of IM-highly-resistant BCR/ABL mutations. Suboptimal response was defined at 3 months (incomplete HR), 6 months (less than partial CgR), 12 months (less than complete CgR), 18 months (less than major molecular response (MMolR)), and in case of MMolR loss, other mutations or other chromosome abnormalities. The importance of regular monitoring at experienced centers was highlighted. 4 INTRODUCTION After the initial descriptions of chronic myeloid leukemia (CML) more than 150 years ago, little meaningful progress was made in its treatment for more than a century. Radiation therapy and busulfan contributed more to improving quality of life than to prolonging survival. Survival prolongation was first achieved with hydroxyurea (HU), and much more with allogeneic hematopoietic stem cell transplantation (alloHSCT) and, later, in a minority of patients with recombinant interferon-alpha (rIFNá)1. Understanding the pathogenesis of the disease began with the discovery of the Philadelphia(Ph) chromosome followed by appreciation of its molecular counterpart, the BCR-ABL fusion gene2,3. Recognition of the tyrosine kinase (TK) activity of the Bcr-Abl proteins led to the discovery of a new series of compounds targeted against BCR-ABL encoded proteins, which inhibited the TK activity, thus aborting the signals controlling the leukemic phenotype4. One of the TK inhibitors, imatinib mesylate (IM) was found to have a high and relatively specific biochemical activity and an acceptable pharmacokinetic and toxicity profile, and thus, was rapidly introduced into clinical practice5-7. This resulted in a revolutionary step in the management of CML and by extension a shift in paradigm for the management of cancer in general. The most recent comprehensive analysis of CML treatment was an evidence-based guideline developed in 1998 by an expert panel convened by the American Society of Hematology (ASH), covering conventional chemotherapy, rIFNá, and alloHSCT8. TK inhibitors were not considered at that time but were subsequently the subjects of editorials and preliminary reviews7,9-14. Although it is premature at this time to perform an evidence-based analysis of the effects of IM, the implications and consequences of the introduction of TK inhibitors are so important that it is not too early to review the available data and to discuss how the treatment of CML could be managed and further progress could be pursued, based upon expert opinion. Therefore the European LeukemiaNet appointed a panel of experts to review the current situation. This report constitutes its opinion. 5 METHODS Panel composition The panel included nineteen members with recognized clinical and research expertise in CML, of whom ten came from the European Union countries (France, Germany, Italy, Spain, Sweden, and the United Kingdom), one from Switzerland, seven from the United States of America, and one from Australia. Scope of the Review The first step was to perform a comprehensive and critical review of the literature after 1998 (the date of the last ASH analysis) was performed. A computerized literature search of the MEDLINE database was conducted in April 2005 and updated in November 2005. Relevant abstracts presented at the 2004 and 2005 meetings of the ASH, the American Society of Clinical Oncology, the European Group for Blood and Marrow Transplantation (EBMT), the European Hematology Association and the International Society for Experimental Hematology were also reviewed. Thereafter, the panel met several times to discuss definition, evaluation and monitoring of the responses, as well as treatment policy. It was agreed that discussion and proposals should be limited to early chronic phase (ECP) patients not only because the treatment of CML patients in a more advanced phase is less amenable to generalizations, but also to focus on the importance of a firstline treatment strategy, late therapeutic interventions being generally less effective. Definitions The criteria that we have used to distinguish CP from accelerated phase (AP) are those that have been used in the most recent treatment reports15-19. These criteria are listed in Table 1, together with WHO criteria, which differs slightly20. The relative risk (RR) of progression and death in early CP (ECP) patients may be calculated by using either the Sokal24 or the Hasford25 formulations (Table 2). 6 WHO Other, and this report – Blast cells in blood or bone marrow (BM) 10-19% – Blast cells in blood or BM 15-29% – Blast cells plus promyelocytes in blood or BM > 30%, with blast cells < 30% – Basophils in blood ≥ 20% – Basophils in blood ≥ 20% – Persistent thrombocytopenia (<100×109L) unrelated to therapy – Persistent thrombocytopenia (<100×109L) unrelated to therapy – Thrombocytosis (>1000×109L) unresponsive to therapy – (not included) – Increasing spleen size and increasing WBC count unresponsive to therapy (not included) – Cytogenetic evidence of clonal evolution (the appearance of an additional genetic abnormalities that was not present at the time of diagnosis) (not included) TABLE 1 – List of the criteria that have been proposed by the World Health Organization (WHO)15 and of the criteria that have been used in most recent studies15-19 and in this review, for defining accelerated phase (AP). The definition of chronic phase (CP) implies that none of these criteria is met. For the definition of blast crisis (BC), the WHO-recommended criteria are the percentage of blast cells in blood or BM (≥ 20%), extramedullary blast proliferation or large foci or clusters of blasts in the bone marrow biopsy20. In recent treatment reports17,21-23, and in this review, the criteria for BC were limited to the percent of blast cells in PB or BM (≥30 rather than ≥20% as for WHO), or extramedullary blast involvement. It should be noticed that the introduction of new treatments could change the boundaries between CP, AP and BC, and modify to some extent the classical subdivision of CML in three phases. 7 SOKAL(24) HASFORD(25) Age (years) 0.116 (age – 43.4) 0.666 when age ≥ 50 Spleen (cm below costal margin, max distance) 0.0345 (spleen – 7.51) 0.042 x spleen Platelet count (׳109/L) 0.188 [(Platelets : 700)2 – 0.563] 1.0956 when platelets ≥ 1500 Blood myeloblasts (%) 0.0887 (myeloblasts – 2.10) 0.0584 ׳myeloblasts Blood basophils (%) Non applicable 0.20399 when basophils > 3% Blood eosinophils (%) Non applicable 0.0413 ׳eosinophils RELATIVE RISK EXPONENTIAL OF THE TOTAL TOTAL ׳1000 LOW <0.8 ≤ 780 INTERMEDIATE 0.8-1.2 781-1480 HIGH >1.2 >1480 TABLE 2 – Calculation and definition of disease relative risk (RR). Sokal risk was defined based on patients treated with conventional chemotherapy24. Hasford risk was defined based on patients treated with rIFNá-based regimens25. We emphasize that calculation of the risk requires use of clinical and hematologic data at diagnosis, prior to any treatment. 8 SUMMARY AND UPDATE OF RECOMBINANT INTERFERON-ALPHA (rIFNá) The superiority of rIFNá-based regimens over conventional chemotherapy was reported previously in the ASH analysis8 and was confirmed in a subsequent study26. A trial of rIFNá vs a combination of rIFNá and low-dose arabinosyl cytosine (LDAC)27 partially confirmed an earlier study28, reporting that the cytogenetic response (CgR) rate was higher with the combination but that overall survival did not differ. A study testing 3 MIU of IFNá three times a week vs 5 MIU/sqm/day indicated that the low dose was as effective and better tolerated than the high dose29. The last updates of the major rIFNá studies reported a 9- or 10-year overall survival (OS) ranging from 27% to 53%30. In one study of 317 patients who had achieved a CCgR, 50% were still in CCgR and 70% were alive after 10 years, with a significant difference in OS between low and high Sokal risk patients (10-year OS 90% vs 40%)31. Residual leukemia was detectable at the molecular level in almost all these patients. Several studies have provided some insights into the biologic and molecular bases of the therapeutic effects of rIFNá30 but there have been no new or updated clinical studies. 9 SUMMARY AND UPDATE OF ALLOGENEIC AND AUTOLOGOUS HEMATOPOIETIC STEM CELL TRANSPLANTATION (HSCT) The ASH panel reported that about 50% of the patients submitted to alloHSCT in first CP from a matched related donor remained alive and leukemia-free after 5 years8. Several subsequent reports confirmed the data and extended the follow up to 10 years, with an OS of 60% and an event-free survival (EFS) of 50%32,33, and to 15 years, with an OS of 47%34 and 52%35. In a meta-analysis of three randomized studies of 316 CP patients, 10-year survival estimates were 63% and 65%36. The Center for International Blood and Marrow Transplant Research (CIBMTR) reported on 4513 patients, with a median age of 35 years, who were transplanted between 1978 and 199737. OS at 18 years was 50% for 3372 first CP patients and 20% for 1141 non-first CP patients. The cumulative incidence of relapse at 18 years was 25% for CP patients and 37% for the others. Relapses were seen up to 21 years after treatment. The longest follow-up of patients transplanted from a matched related donor is that reported by the EBMT, on 2628 patients transplanted between 1980 and 199038. OS at 20 years was 34% for all patients, 41% for patients transplanted in first CP from an HLA-identical sibling, and 49% for those who had an EBMT risk score (see below) of 0-1. In children, 10-year OS estimates were reported to be 65-70%39. An EBMT survey analyzed 3142 patients submitted to conventional alloHSCT in any phase of CML and from any donor40. This analysis led to the formulation of a prognostic score subsequently validated by two other analyses41,42. Depending on the risk score, survival ranged from 72% to 11% in all patients and from 70% to 25% in the patients who were transplanted in ECP (Table 3). Progress in molecular DNA typing of HLA alleles, in the management of opportunistic infections and in supportive care, as well as modifications and improvement of conditioning regimes and immunosuppresive therapy, have contributed to improved results of alloHSCT, using both family members and unrelated donors43. For CML patients receiving conventional transplants, the use of peripheral blood stem cells has not been shown to be better than the use of marrow cells44. 10 Reduced intensity conditioning (RIC) is currently being evaluated for CML45-48. The EBMT has reported on registry data of 187 patients (median age 50 years) who were submitted to RICalloHSCT, between 1994 and 2002, mainly from matched related donors49. Three-year OS was 70% for the patients with an EBMT score of 0-2, 50% for the patients with a score of 3-4, and about 30% for those with a score ≥ 5. The use of RIC may permit transplantation also in older patients, but the long term impact of these and other experimental procedures of alloHSCT on OS, EFS and quality of life cannot yet be assessed. The role of treatment intensification with autologous HSCT (autoHSCT) rescue has been the subject of a number of studies and reviews covering a period of more than 20 years50. Several observations suggested that the procedure was useful to achieve more remissions and to prolong survival. Several randomized studies were initiated but none was completed. A meta-analysis of six such trials in which patients were randomly allocated to receive autoHSCT or a rIFNá-based regimen did not show an advantage for autoHSCT51. 11 PROGNOSTIC FACTORS RISK SCORE Age 0 if < 20 years 1 if 20 – 40 years 2 if > 40 years Interval from diagnosis to HSCT 0 if ≤ 1 year 1 if > 1 year Disease phase 0 if chronic 1 if accelerated 2 if blastic Donor-recipient sex match 1 if female donor and male recipient 0 if any other match Donor type 0 if HLA-identical sib 1 if any other TOTAL RISK SCORE 5-YEAR OVERALL SURVIVAL EBMT series CIBMTR series, all patients CIBMTR series, ECP patients 0 – 1 72% 69% 70% 2 62% 63% 67% 3 48% 44% 50% 4 40% 26% 29% 5 – 7 22% 11% 25% TABLE 3 – EBMT transplantation risk score. The table lists the prognostic factors and the corresponding risk score, and reports five-year overall survival rates, as they were calculated in the original EBMT (European Group for Blood and Marrow Transplantation) report40 and in the subsequent CIBMTR (Center for International Blood and Marrow Transplant Research) study41. All EBMT and CIBMTR patients were treated by conventional alloHSCT procedures between 1989 and 1997. Leukemia free survival (calculated only in the EBMT study) at 5 years was 61% for risk 12 score 0-1, 47% for risk score 2, 37% for risk score 3, 35% for risk score 4, and 19% for risk score 5- 7. 13 SUMMARY AND UPDATE OF IMATINIB (IM) DATA IM vs rIFNá in ECP The superiority of IM 400 mg daily over rIFNá and LDAC was established in a prospective randomized international study of 1106 ECP patients (IRIS study). IM was superior to rIFNá for efficacy, with a complete hematologic response (CHR) rate of 95% vs 55%, a complete CgR (CCgR) rate of 76% vs 15% and progression free survival (PFS, survival free from progression to AP/BC) at 19 months of 97% vs 91% (P < 0.001). It was better also for compliance, toxicity, and quality of life17,52. As expected, molecular response (MolR) rates were also significantly better, with an estimated major MolR (MMolR) rate at 12 months of 40% vs 2%53. Since many patients who had been assigned to rIFNá and LDAC were crossed over to IM, it is difficult to meaningfully compare the long term results of the two treatment arms. However, two independent retrospective analyses provided independent confirmation that IM was better than any other non-transplant treatment54,55. Studies have shown that IM is a cost-effective first line therapy compared to rIFNá56. Follow-up clinical results in ECP When IM was given at 400 mg daily for initial treatment of ECP patients, the CHR rate after one year was 95% and the CCgR rate was 76%17. Of those patients who had achieved a CCgR, a MMolR was achieved in 57% (40% of the patients who had been assigned to IM)53. The proportion of MMolR patients was reported at 55% of all patients, after two years57. After 54 months followup, PFS was 93%, OS was 90%, and survival freedom from progression to AP/BC as well as from hematologic or cytogenetic relapse was 84%58. Currently, this survival outcome is better than for 14 any other reported treatment. The annual rate of progression to AP/BC appeared to be fairly constant during the first 4 years of treatment, namely 1.5%, 2.8%, 1.6%, and 0.9% 58. Clinical results in late chronic phase (LCP), accelerated phase (AP) and blast crisis (BC) Before IM was initially administered as first line treatment for CML, it was given to patients who were in CP, but resistant or intolerant to rIFNá or who had been treated with conventional chemotherapy. These patients are classified as “late CP” (LCP). Four international studies reported a CCgR rate ranging from 41% to 64% with a 5-year PFS of 69% and a 4-year OS of 86- 88%15,18,19,23,59-61. Moreover, one retrospective analysis found that survival of LCP IM-treated patients was superior to that of historical controls, even when a CCgR was not achieved62. For AP patients the best results were achieved at a daily dose of 600 mg, with a CHR rate of 37% , a CCgR rate of 19% and a 3-year PFS of 40%17,63. In BC the rate of CHR was about 25% and several responders achieved also a CCgR, but PFS was short, with a median of 10 months or less, and only 7% remained alive after 3 years5,21-23, 63, 64. Molecular response (MolR) Since the frequency of CCgR is very high in IM treated patients, it is necessary to measure the level of the BCR-ABL transcripts to determine minimal residual disease (MRD) (FIGURE 1). In about 50% of all patients, corresponding to about 70% of the patients who have achieved a CCgR, a substantial reduction, commonly referred to as a 3-log reduction from a standard baseline or “major molecular response” (MMolR), was reported in ECP53,65-67, while in LCP the responses were consistently lower19,20,67,68. The actual frequency with which no residual BCR-ABL transcripts can be detected by use of the most sensitive available methods, sometimes imprecisely referred to as “complete” MolR (CMolR), is very variable, and ranges from 4% to 34%18,19,57,67,69. The rate at 15 which the BCR-ABL transcript levels continue to fall reduces with time57,70,71. This is consistent with the reports that Ph+ stem cells may be less sensitive to IM than later Ph+ progenitors72-75. The question of whether the inability to detect BCR-ABL transcripts over the long-term is consonant with “cure” cannot yet be answered. Some case reports suggest that the disease may recur shortly after IM discontinuation, so that until more information becomes available IM treatment should not be discontinued without reasons76-80. Dose issues The issue of the optimal dose of IM is not yet settled. In early studies for drug registration the maximum tolerated dose was not identified. A dose of 300 mg daily was sufficient to achieve a CHR in almost all LCP patients and at 400 mg daily the blood concentration of IM was consistently higher than that required to inhibit 50% of Bcr-Abl TK activity in vitro81,82. It was also found that a daily dose of 600 mg was likely to be more effective than 400 mg for AP/BC patients16,21 and that increasing the IM dose to 600 or 800 mg could benefit a subgroup of patients with inadequate response or disease progression83. Since at higher concentrations IM may inhibit more effectively unmutated Bcr-Abl and some mutants, studies were initiated to test higher doses also in CP. In patients with both prior hematologic and cytogenetic resistance to 400 mg of IM daily, increasing the IM dose to 800 mg resulted in a CHR in 65% of patients and a CCgR in 18%84. In LCP patients who had not received prior IM, 66% achieved a CCgR85. In ECP patients a CCgR was achieved in 90% of patients, with 30% CMolR86. In a multicenter Australian study of IM-naive ECP patients whose dose was escalated from 600 to 800 mg daily, the CCgR rate and the MMolR rate were 81% and 53%70,87. These studies had no controls and the median follow up was short (6 to 16 months). Thus, whether increased doses of IM,compared to standard dose of IM, will achieve an increased overall number of CCgR and MMolR, or whether these effects will merely occur only earlier, remains to be determined. Answers are expected from prospective studies that are in progress13,88,89. 16 In contrast no studies have yet explored the response to lower IM doses, probably because the 400 mg dose is usually well tolerated and several reports have discouraged the use of low IM doses because of the possible development of resistance18,19,58,59,66. Combination with other drugs Since rIFNá and AC are effective in the treatment of CML and since their mechanisms of action differ, the combinations of IM with rIFNá and with AC were the first to be tested. In an exploratory study of 77 patients, the combination of IM 400 mg daily with pegylated rIFNá2b (PegIntron, Schering Plough), 50 to 150 ìg weekly, was administered66. The compliance to the combination was limited, since the median tolerated dose of rIFNá was only 35 ìg/week and 50% of patients discontinued rIFNá before the end of the first year of treatment; after one year the CCgR and the MMolR rates were 70% and 48%66. The combination of IM 400 mg with LDAC has been investigated in 30 ECP patients90; at one year the CCgR rate was 70% , with grade 3 and 4 hematologic toxicity in 53% of patients. Prospective randomized studies of IM alone vs IM in combination with rIFNá, LDAC and high dose AC are ongoing13,89,91. Several drugs have been shown to overcome IM resistance or to synergize with IM in preclinical models, including leptomycin B, proteasome inhibitors, mTOR-inhibitors, arsenic trioxide, mycophenolic acid, farnesyl-transferase inhibitors, bryostatin, decitabine, histone-deacetylase inhibitors, homoharringtonine, and phosphoinositol-dependent kinase-1 inhibitors92-106, but results are still preliminary and limited107-110. 17 Relationship with allogeneic hematopoietic stem cell transplantation (alloHSCT) Treatment with IM prior to alloHSCT was not reported to be associated with an increase of transplant related morbidity and mortality111-115. IM was also found to control leukemia in patients relapsing after alloHSCT116,117. In a multicentric retrospective study of 128 patients, the CCgR rates were 58% in CP, 48% in AP, and 22% in BC, with molecular negativity in 37%, 33%, and 11% of cases respectively118. In patients treated in early molecular relapse after alloHSCT, molecular negativity was reinduced in 15/18 cases78. A synergy of IM with donor lymphocyte infusion has been suggested119. Factors affecting drug concentration in target cells Several factors can influence IM concentration in target cells, including intestinal absorption, liver metabolism through cytochrome P450 isoenzyme-3A4, plasma binding to á1-acid-glycoprotein, and the transporters involved in multidrug resistance. P-glycoprotein (Pgp) was found to influence IM intracellular concentration in some studies120-125 but not in others126,127. Interestingly, some studies have suggested that Pgp inhibition restored IM sensitivity120,124,125 IM does not cross the blood brain barrier128 Also, the expression of the organic cation transporter hOCT was reported to influence intracellular drug concentration123. Resistance and mutations Resistance may be multifactorial, including BCR-ABL mutations of the kinase domain interfering with IM binding, BCR-ABL amplification or overexpression, clonal evolution and decreased IM biovailability or cell exposure120,130-141. Clonal evolution and mutations (Table 4) are likely to be the most important factors and are related to each other133,142. The frequency of BCR-ABL mutations in 18 resistant patients was reported to range from 42%139 to 90%133 depending on the methodology of detection, the definition of resistance and the phase of the disease. Mutations are found more frequently in AP/BC. In CP patients they are rarer and were identified more frequently in patients with more than 2-fold increase of the BCR-ABL transcript levels than in those with stable or decreasing levels143. However, mutant Ph+ sub-clones may remain at low levels, may be transient or unstable and may not be consistently associated with subsequent relapse144,145. In many cases the mutations have been detected in samples that were collected during IM treatment, but in several cases the mutation was also traced back to samples collected before treatment, especially in cases of AP/BC133,146,147. With more sensitive techniques, mutations were also found in some cases of IMnaive patients and in patients who were in CCgR147-149. It is important to note that Ph+ primitive cells have been reported to be less sensitive to IM in vitro and in vivo, to harbor BCR-ABL mutations even prior to IM exposure and to develop rapidly mutations under IM pressure72,74,147,149- 151. Not all mutations have the same biochemical and clinical properties (Table 4). The T315I mutation and some mutations affecting the so-called P-loop of BCR-ABL confer a greater level of resistance, whereas the biochemical resistance of other mutations can be overcome by a dose increase, and some mutations are functionally irrelevant133,137-140,152,153. Thus, the detection of a kinase domain mutation must be interpreted within the clinical context. 19 imatinib IC50 (nM) BCR-ABL Biochemical Cellular Wild-type 300 260-500 M244V 380 2000 L248V n.a. 1500 G250E 1000 1350-3900 Q252H n.a. 1200-2800 Y253F >5000 3475 Y253H* >5000 >10000 E255K 2800 4400-8400 P-loop E255V >5000 >5000 D276G n.a. 1500 T277A n.a. n.a. F311L 775 480 F311I n.a. n.a. T315I* >5000 >10000 F317L* 900 810-1500 M343T n.a. n.a. M351T 820 930 M351V n.a. n.a. E355D n.a. n.a. E355G n.a. 400 Catalytic domain F359V* 4700 1200 V379I 800 1630 A380T* 340 2450 F382L n.a. n.a. L387M 1500 1000 L387F n.a. 1100 H396P 340-800 850-4200 Activation loop H396R 1950 1750 S417Y n.a. n.a. E459K n.a. n.a. F486S 1230 2800 Table 4 – IC50 values of BCR-ABL mutations observed in patients resistant to IM154. Shaded boxes highlight residues belonging to the P-loop, catalytic domain and activation loop, as indicated. Residues marked with an asterisk (*) represent IM contact sites. Other mutations which have not yet been detected in patients were recovered from in vitro saturation mutagenesis screenings for mutations conferring resistance to IM or other TK inhibitors. They include: M237I, G250A, G250V, E255D, A269V, E281K, E282D, K285N, V289S, V299L, T315A, F317C, V338G, Q346H, S348L, M451L, E352K, E355A, A366D, G398R, G463D, M472I, E494A, with a cellular IC50 20 <1460 nM (that is the mean trough plasma level of IM in patients treated with 400 mg daily), and E255R, E275K, M278L, E279K, E281K, E292Q, Q300H, F311V, T315S, E316D, G321W, D325N, A380S, L384M, M388L, E450K, E499K, with a cellular IC50 >1460 nM . IC50 is the concentration that inhibits by 50% the biochemical TK activity of BCR/ABL and suppresses by 50% the growth of Ph+ cell lines. n.a., not available. 21 Additional chromosome abnormalities (ACA) in Ph+ cells (clonal evolution) and other chromosome abnormalities (OCA) in Ph- cells Within the Ph+ clone additional chromosome abnormalities (ACA) can be found in a variable proportion of metaphases and in a variable number of patients. This phenomenon, also known and described as clonal evolution, is rare in ECP and becomes more frequent over time and with disease progression23,134,155-160. A negative relationship of ACA with IM response has been shown, including a lower CgR rate157, a higher hematologic relapse rate (50% vs 9%)155 and a shorter OS (75% vs 90% at 2 years)156. Chromosome 9q+ deletions (del9q+) were reported to be associated with less CHR, less CgR and a shorter PFS in LCP, AP and BC patients in one study161 but not in another162. Other chromosome abnormalities (OCA) have been reported in the Ph- cells of about 5% of the patients who had achieved a CCgR with IM166-170. Many of these patients were in LCP and had been pretreated with rIFNá based regimens. OCA included trisomy 8 alone in about 50% of such cases, trisomy 8 with other abnormalities in about 10% of cases, a deletion of chromosome 7 alone or with other abnormalities in about 15% of cases, and other abnormalities in the remaining cases. The balance between the Ph+ clone and the Ph- clone with OCA fluctuated depending on IM treatment, which suppressed Ph+ cells and allowed the Ph- clone with OCA to expand. In some cases Phclone with ACA were reported to be associated with a myelodysplastic syndrome, mainly in patients with a deletion of chromosome 7 and/or other complex abnormalities but also in patients with isolated trisomy 8. It was also reported that many patients remained in complete cytogenetic and hematologic response after the detection of OCA and that OCA may be transient166,167,169,170 but the follow-up is still short. 22 Prognostic factors Two sets of prognostic factors can be considered, namely those that can be identified prior to treatment (baseline factors) and those that can be identified during the treatment (response-related factors). The main baseline factors are the phase of disease and the relative risk (RR). Although different definitions of AP and BC have been used (Table 1), the phase of the disease influences strongly the response, the duration of the response and OS, with better results in CP than in AP and in AP than in BC. The RR, either by Sokal’s24 or Hasford’s methods25, predicts the cytogenetic response to IM 400 mg daily (Table 5) 53,171,172. Moreover, Sokal’s RR has been reported to predict also MolR and OS. In the IRIS study, the rate of 12-month MMolR among CCgRs was 66%, 45% and 38% in low, intermediate and high risk patients respectively (P = 0.007)53. The OS at 54 months was 94%, 88% and 81% for low, intermediate and high Sokal risk patients (P <0.001)58. These risk definitions which were derived from patients treated with conventional chemotherapy or IFNá, are still useful and should be used until further studies identify and confirm other factors of possible prognostic relevance, such as genomic profile173-177, genetic polymorphisms178,179, Wilms tumor gene expression180, total phosphotyrosine levels in CD34+ cells181 and the phosphorylation level of the adaptor protein Crkl182. In addition, it has been reported that BCR-ABL expression levels affect the CgR to IM19 and determine the rate of development of resistance to IM141. ACA, including Ph duplication, and del9q+, are also candidate adverse prognostic factors. As data from IRIS study are continuously updated58,172,183, early cytogenetic response seems to be the most important response-related prognostic factor (Table 6). If no CgR is achieved after 3 months, there is still a 50% chance of achieving a CCgR later on. If there is any (even minimal) CgR after 6 months of treatment, there is still a fair chance of achieving a CCgR later on, but if the 6-month karyotype remains more than 95% Ph+, the probability is only 15%. After 12 months of treatment, if the CgR is partial the probability of achieving a CCgR at 2 years is still 50%, but if the 23 response is less than partial, this probability becomes less than 20%. The data reported in Table 6 also highlight the relationship between early CCgR and EFS. The level of MolR was also found to be an important dynamic factor of prognosis. It was reported that transcript levels after 1 or 2 months of treatment predicted late responses184,185, that a low level of residual disease was associated with continuous remission68, and that a MMolR after 12 months of treatment was associated with a better EFS and PFS53,58. A rise of BCR/ABL transcript level has been consistently associated with mutations or response loss143,186. 24 Complete cytogenetic response Relative Risk Low Interm High Italian multicenter study, 77 patients, IM 400 mg, response at 6 months171 70% 41% 8% International multicenter IRIS study, 383 patients, IM 400 mg – response at 12 months53 76% 67% 49% – response at 42 months172 91% 84% 69% Single-center study, 187 patients, IM 400-800 mg, overall response54 84% 85% 69% TABLE 5 – Cytogenetic response by relative risk. Two independent studies of newly diagnosed, ECP patients who were treated initially with IM 400 mg daily have shown that the cytogenetic and the molecular response to that dose of IM was significantly related to Sokal’s risk. In one study171 the relationship was found also using Hasford’s risk. In another study54 the differences were not significant, but IM dose was higher, 800 mg in 100 patients, 600 mg in 14 patients, and 400 mg in 73 patients. The last update of the IRIS study58 reported OS was also risk related, being 94% for low risk patients, 88% for intermediate risk patients and 81% for high risk patients (P < 0.001), after 54 months of therapy. 25 Months on treatment Cytogenetic response Probability of CCgR at 2 years EFS at 42 months Partial 90% NA 3 Minor 60% NA Minimal/None 50% NA Complete NA Partial 80% 95% Minor or Minimal 50% 6 None 15% 75% Complete NA 12 Partial 50% 90% Minor/Minimal/None <20% 65% TABLE 6 – Relationship between the degree of early CgR, the CCgR rate at 2 years, and EFS at 42 months in IRIS study172,183. From the same study it was reported that after 54 months, survival free from progression to AP/BC was 97% for the patients with a CCgR at 12 months, 95% for those with a PCgR and 81% for those who at 12 months had achieved less than a PCgR58. NA = Not applicable or not available. 26 DEFINING AND MONITORING THE RESPONSE Hematologic Response (HR) and Cytogenetic Response (CgR) In almost all recent reports on the treatment of CML, HR and CgR were defined virtually the same way, and with only minor differences15,17-19,26-29,66. We propose to use the definitions that are listed in Table 7. We recommend that HR be evaluated every 2 weeks until a CHR has been achieved and confirmed, and a conventional cytogenetic examination of marrow cells be performed before treatment, at least every 6 months until a CCgR has been achieved and confirmed, then every 12 months. Once a MMolR has been achieved and confirmed, conventional cytogenetic examination of marrow cells may be performed less frequently, depending on clinical, hematologic and molecular findings. Fluorescence-In-Situ-Hybridization (FISH) on interphase cells has the potential advantage of evaluating many more cells and of using peripheral blood instead of marrow187,188, but since the data obtained so far are all based on conventional cytogenetics, we recommend using FISH only before treatment, to identify cases of Ph-, BCR-ABL+ CML, and those with variant translocations, Ph amplification or del9q+. Molecular response (MolR) The necessity for a quantitative definition of MolR has developed with the introduction of IM, because with IM most patients achieve a CCgR, so that molecular methods for measuring minimal residual disease (MRD) are required (Figure 1). The IRIS trial provided evidence for the first time that a reduction of BCR-ABL transcripts by 3 or more logs below a standard baseline value correlated with PFS53. The use of the “log reduction” terminology has led to some degree of 27 confusion since it seems to imply that the value is a relative one. For this reason, at a consensus conference held in Bethesdaunder the auspices of the NIH, it was proposed to move away from the term “log reduction” and to introduce a standardized numerical International Scale (IS) expressing the amount of BCR-ABL as a percentage of a control gene and anchored to two “absolute” values based on validated reference materials (plasmids, lyophilised cells or cell extracts) of known value189. The first value will be designated 100% on the proposed IS and the second value will represent a 3-log reduction, i.e. 0.1%. A given laboratory will use the validated reference material to determine the local value that is equivalent to MMolR as determined in the IRIS trial. By comparing the value for a 3-log reduction with the value on the internationally agreed scale, each laboratory can derive a conversion factor which can then be used to express the results in any given patient on the IS. In ECP patients, evaluating MRD with real-time quantitative polymerase chain reaction (RQ-PCR) does not require bone marrow cells. Blood is drawn, e.g. 10 ml, which contains a sufficient amount of leukocytes for RNA extraction from the whole buffy coat. We propose RQ-PCR on peripheral blood cells be performed at regular intervals of 3 months, even after RQ-PCR becomes negative. Assessing the molecular status of a patient is not limited to the evaluation of the level of the BCRABL transcripts. We propose performing a mutational analysis immediately in any case of treatment failure or suboptimal response, including a confirmed rise of BCR-ABL transcript level. We recognize, however, that there is currently no consensus regarding the degree of increase which should cause concern189 and that there is at present only a limited number of laboratories worldwide currently performing these analyses. 28 HEMATOLOGIC RESPONSE (HR) CYTOGENETIC RESPONSE (CgR) MOLECULAR RESPONSE (MolR) (BCR/ABL to control gene ratio according to the international scale) Complete – Platelet < 450×109L – WBCC < 10 x109L – Differential without immature granulocytes and with less than 5% basophils – Non palpable spleen Complete Ph+ 0 Partial Ph+ 1-35% Minor Ph+ 36-65% Minimal Ph+ 66-95% None Ph+ > 95% “Complete” = transcript non quantifiable and non detectable Major ≤ 0.10 Check every 2 weeks until a complete response has been achieved and confirmed, then every 3 months unless otherwise required Check at least every 6 months until a complete response has been achieved and confirmed, hence at least every 12 months Check every 3 months Mutational analysis in case of failure, suboptimal response, or transcript level increase TABLE 7 – Response definition and monitoring. Complete HR (CHR), complete CgR (CCgR) and major MolR (MmolR) should be confirmed in two subsequent occasions. CgR is evaluated by morphologic cytogenetics of at least 20 marrow metaphases. FISH of peripheral blood cells should be used only if marrow cells cannot be obtained. MolR is assessed on peripheral blood cells. The international scale for measuring MolR is that proposed by Hughes et al189. 29 Failure and suboptimal response The goals of treatment, in order of time and importance, are CHR, CCgR, MMolR, and “complete” molecular response. Although the time to response may not always affect the prognosis, it is operationally useful to define at which time point a response may be satisfactory, thus encouraging continuation of current treatment, or if it is not satisfactory, thus requiring or suggesting a change in the therapeutic strategy. Based on the available information, as summarized in prior sections, we propose to define the response to the treatment at different time points as “failure” and “suboptimal”. In this context “failure” means that continuing IM treatment at the current dose is no longer appropriate for these patients, who would likely benefit more from other treatments. “Suboptimal response” means that the patient may still have a substantial benefit from continuing IM, but that the long-term outcome of the treatment would not likely be as favorable. Moreover, we propose that some factors should “warn” that standard dose IM treatment may not be the best choice and that patients with these factors requires a more careful monitoring. The proposed criteria for failure, suboptimal response and warning are listed in Table 8. 30 TIME FAILURE SUBOPTIMAL RESPONSE WARNINGS Diagnosis NA NA – High risk – Del9q+ – Additional chromosome abmormalities (ACA) in Ph+ cells 3 months – No hematologic response (HR) (stable disease or disease progression – Less than Complete HR (CHR) 6 months – Less than Complete HR (CHR) – No cytogenetic response (CgR) (Ph+ more than 95%) – Less than Partial CgR (PCgR) (Ph+ more than 35%) 12 months – Less than PCgR (Ph+ more than 35%) – Less than Complete CgR (CCgR) – Less than major MolR (MMolR) 18 months – Less than CCgR – Less than MMolR Any time – Loss of CHR (1) – Loss of CCgR (2) – Mutation (3) – ACA in Ph+ cells (4) – Loss of MMolR (4) – Mutation (5) – Any rise in transcript level – Other chromosome abnormalities in Phcells (1) To be confirmed on two occasions unless associated with progression to AP/BC (2) (2) To be confirmed on two occasions, unless associated with CHR loss or progression to AP/BC (3) High level of insensitivity to IM (4) To be confirmed on two occasions, unless associated with CHR or CCgR loss (5) Low level of insensitivity to IM 31 TABLE 8 – Operational definition of failure and suboptimal response for previously untreated, ECP, CML patients who are treated with IM 400 mg daily. Failure implies that the patient should be moved to other treatments whenever available. Suboptimal response implies that the patient may still have a substantial benefit from continuing IM treatment, but that the long term outcome is not likely to be optimal, so that the patient becomes eligible for other treatments. Warnings imply that the patient should be monitored very carefully and may become eligible for other treatments. The same definitions can be used to define the response after IM dose escalation. For risk definitions refer to Table 2. For mutations refer to Table 4. For the definition of HR, CgR and MolR, refer to Table 7. Abbreviations: ACA = Additional Chromosome Abnormalities; HR = Hematologic Response; CHR = Complete Hematologic Response; CgR = Cytogenetic Response; PCgR = Partial Cytogenetic Response; CCgR = Complete Cytogenetic Response; MMolR = Major Molecular Response; NA = Not Applicable.
33 TREATMENT POLICY Standard (non-investigational) treatment of ECP Ph+ CML includes HU, rIFNá±LDAC, IM 400 mg daily and alloHSCT. The superiority of IFNá±LDAC over HU was already demonstrated and confirmed8,30. The superiority of IM 400 mg over IFNá±LDAC has also been demonstrated17,53. Standard alloHSCT is a recognized therapeutic procedure achieving long lasting molecular remissions or cures in about 50% of the patients who are eligible for the procedure, with substantial differences among recognized risk groups40,41. In countries where IM is available and standard alloHSCT is feasible we are now in a rather privileged situation to have two potent strategies which are both established but are neither perfect nor mutually exclusive. IM is preferred as initial treatment. In a patient with a high disease risk and a low EBMT risk score the choice between IM and alloHSCT should be discussed, but there is little reason to deny such a patient a trial with IM since the early response to IM can either reinforce or weaken the indication for alloHSCT. The motivations for treatments other than IM are intolerance or excess toxicity, failure, suboptimal response, and “warnings”. In case of intolerance or excess toxicity, the choices are either alloHSCT or rIFNá±LDAC, which must be weighed against investigational trials of new agents and should follow the principle of shared decision-making wherein the patient is explained the risks and rewards of each treatment decision. In case of failure (Table 8 ) we propose that the first choice be alloHSCT, or dose-escalation of IM to 600 or 800 mg daily, provided that the patient tolerated 400 mg and that resistance to IM was not associated with a BCR-ABL mutation with a high level of insensitivity to IM. In case of suboptimal response (Table 8) we propose that the first choice be dose-escalation of IM to 600 or 800 mg daily, provided that the patient tolerated 400 mg. AlloHSCT could be offered to patients with a low or intermediate EBMT risk score and high RR or other warning features. 34 In patients presenting with “warning” features, standard treatment is still IM 400 mg, but any “warning” (Table 8) should alert that the patient may become eligible for IM dose escalation, for alloHSCT, or in selected cases for investigational agents. There are several other possible scenarios. The first is the patient in whom other treatment options are not available; in such case the choice would be between continuing IM treatment, if a CHR is maintained, or to resort to HU. The second scenario is the patient requiring IM dose reduction or frequent treatment discontinuations. We recommend that the treating physician advise the patient to adhere to the 400 mg dose insofar as possible; appropriate supportive care should be provided, including myeloid growth factors and erythropoietin; the response should be monitored frequently. Monitoring of blood IM concentration is not required, but it would be desirable in case of failure, in patients who must take drugs interfering with cytochrome P450, and in those who experience a severe drug-related adverse event. The proposals and recommendations discussed in this paper focus on ECP patients but sometimes patients are first diagnosed when initially in AP or BC. There are few data pertaining to treatment results in these patients. We propose patients in early BC to be treated initially with IM or other TK inhibitors (based on mutational analysis) and then to proceed to alloHSCT. Since some temporal latitude exists after the diagnosis of AP, a more prolonged trial with IM is possible. 35 CONCLUSIONS Progress in drug development, in molecular and cellular biology and in HSCT obliges the medical community to maintain a critical attitude to the management of Ph+ CML. On the one hand it must be recognized that the introduction of IM has marked an important and hopefully revolutionary step, but the long term outcome of this treatment cannot yet be assessed. On the other hand alloHSCT holds the promise of cure, but with definite toxicity and mortality. At the same time other TK inhibitors and targeted agents are already in preclinical and clinical evaluation13,154,190-194. The proposals described in this report have been generated by a panel of experts to strike a balance between the magic freedom of research in progress and the practice of advising patients and managing treatment. The proposals concerning treatment policy may be provisional, in the absence of the evidence that will be provided only by longer follow-up of prospective studies; however, the recommendations concerning the methods that must be used to evaluate and to monitor the response are nonetheless cogent. Cytogenetic and molecular monitoring, including mutational analysis, is expensive and requires appropriate resources and sophisticated facilities. However the cost of monitoring is negligible by comparison with the cost of treatment, whether it is a targeted agent or HSCT. Moreover, careful monitoring is required to ensure that an individual patient receives the proper treatment and to decide if and when a therapy should be changed. Finally, it should be realized that progress makes treatment more effective but not necessarily easier. Thus the treatment of Ph+ CML should be provided under the guidance of an experienced center, offering and asking patients to be registered on investigational studies. This is necessary to ensure that all the data, clinical and biological, that are urgently required to answer the present questions, are collected and analysed in an accurate and timely manner, for the benefit of the subsequent patients and for further progress in the treatment of leukemia. 36 Diagnosis, Pretreament or Hematologic Relapse Complete Hematologic Response Undetectable transcript (Complete Molecular Response) Complete Cytogenetic Response Major Molecular Response 100 10 1 0.1 0.01 0.001 0.0001 BCR-ABL ratio (according to the International Scale) 1012 1011 1010 109 108 107 106 Number of leukemic cells 37 Figure 1 – Approximate relationship between response, the putative number of leukemic cells and the level of BCR-ABL transcripts. 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