immune modulation of minimal residual disease in early chronic phase chronic myelogenous leukemia :...

Immune Modulation of Minimal ResidualDisease in Early Chronic Phase ChronicMyelogenous LeukemiaA Randomized Trial of Frontline High-Dose Imatinib Mesylate With or Without PegylatedInterferon Alpha-2b and Granulocyte-Macrophage Colony-Stimulating Factor

Jorge Cortes, MD; Alfonso Quintas-Cardama, MD; Dan Jones, MD; Farhad Ravandi, MD; Guillermo Garcia-Manero, MD;

Srdan Verstovsek, MD; Charles Koller, MD; Jody Hiteshew, MD; Jenny Shan, PhD; Susan O’Brien, MD;

and Hagop Kantarjian, MD

BACKGROUND: Most patients with chronic myelogenous leukemia (CML) harbor residual disease, as evidenced by

molecular techniques even after treatment with high-dose imatinib (ie, 800 mg/d). Interferon alpha (IFN a) is effica-

cious in CML likely due to its immunomodulatory properties, and is synergistic in vitro with imatinib and granulocyte

macrophage-colony stimulating factor (GM-CSF). METHODS: A study was undertaken to determine whether adding

pegylated (PEG) IFN a-2b and GM-CSF to high-dose imatinib may improve the complete molecular response rate in

patients with CML in chronic phase. Ninety-four patients were treated with imatinib 800 mg/d for the first 6 months,

then randomly assigned to continue high-dose imatinib alone (n ¼ 49) or in combination with PEG IFN a-2b 0.5 lg/kg/wk and GM-CSF 125 mg/m2 3� weekly (n ¼ 45). RESULTS: The median follow-up for all patients was 54 months

(range, 7-70 months). There were no differences in the rates of complete cytogenetic response (87% vs 90%; P ¼1.0), or of major (77% vs 77%; P ¼ 1.0) or complete (11% vs 13%; P ¼ 1.0) molecular response (on the international

scale) at 12 months between the 2 arms, or at any time during the study. Adverse events led to PEG IFN a-2b discon-

tinuation in all patients. CONCLUSIONS: The addition of PEG IFN a-2b and GM-CSF to high-dose imatinib therapy

does not improve significantly the cytogenetic or molecular response rates compared with high-dose imatinib alone.

The high dropout rate in the PEG IFN a-2b arm may have compromised its potential immunomodulatory benefit.

Cancer 2011;117:572–80. VC 2010 American Cancer Society.

KEYWORDS: chronic myeloid leukemia, granulocyte-macrophage colony-stimulating factor, imatinib, immune

modulation, interferon alpha-2b.

Standard dose imatinib mesylate therapy (ie, 400 mg/d) is associated with complete hematologic response (CHR)and complete cytogenetic response rates of 98% and 82%, respectively, in patients with chronic myeloid leukemia (CML)in chronic phase.1 High-dose imatinib (ie, 800mg/d) renders complete cytogenetic response rates of 89% in chronic phaseCML after interferon-alpha (IFN a) failure,2 and of 90% in newly diagnosed chronic phase CML.3 Achieving a completemolecular response (ie, undetectable BCR-ABL) may further improve event-free survival (EFS) and overall survival (OS).4

Alternatively, patients who fail to achieve a major molecular response (ie, 3-log reduction or �0.1%) may have anincreased risk of losing their cytogenetic response,5 and of developing ABL1 kinase domain mutations.6 Most patientstreated with imatinib harbor residual molecular disease, which supports the notion that imatinib fails to eradicate quies-cent BCR-ABL1-positive stem cells.7-9

IFN a produces complete cytogenetic response rates ranging from 5% to 27%,10-13 and many of those who achieveda major molecular response have not progressed after long-term follow-up (even after IFN a discontinuation),14 whichhas been linked to the immunomodulatory properties of IFN a.15 IFN a synergizes in vitro with imatinib,16 which sug-gests that IFN amay enhance the clinical activity of imatinib. Pegylated (PEG) IFN a-2b, a more tolerable form of IFN a

DOI: 10.1002/cncr.25438, Received: November 23, 2009; Revised: February 7, 2010; Accepted: March 9, 2010, Published online September 30, 2010 in Wiley

Online Library (wileyonlinelibrary.com)

Corresponding author: Jorge Cortes, MD, Department of Leukemia, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 428,

Houston, TX 77030; Fax: (713) 794-4297; [email protected]

Department of Leukemia, The University of Texas M. D. Anderson Cancer Center, Houston, Texas

572 Cancer February 1, 2011

Original Article

with a longer half-life, in combination with imatinib ren-dered major cytogenetic response rates of 80% at 6months in the frontline setting, and of 60% in patients af-ter IFN a failure, suggesting in vivo synergism.17 Thecombination of IFN a and granulocyte-macrophage col-ony-stimulating factor (GM-CSF) is a potent stimulus ofdendritic cell differentiation of CML mononuclearcells.18 The addition of GM-CSF to IFN a has beenreported to be well tolerated and has resulted in excellentresults compared with other IFN a-based regimens inearly chronic phase CML.19,20 Based on these data, wedesigned a randomized phase 2 study to investigatewhether adding PEG IFN a-2b and GM-CSF to high-dose imatinib would increase the rate of major molecularresponse and prolong remission duration in patients withearly chronic phase CML compared with high-dose imati-nib therapy.

MATERIALS AND METHODS

Eligibility Criteria

Patients aged�18 years with CML in early chronic phase(<12 months from diagnosis) were eligible. Except forhydroxyurea, patients should have received no or minimalprior therapy (<1 month of IFN a and/or standard-doseimatinib). Other eligibility criteria were: 1) performancestatus �2 by the Eastern Cooperative Oncology Groupscale; 2) serum creatinine and total bilirubin <1.5� theupper limit of normal; 3) patients with clonal evolutionwere eligible in the absence of other signs of acceleratedphase (AP); 4) women of childbearing potential wererequired to practice effective contraception methods; and5) signed informed consent.

Treatment Schedule

Patients were randomized to 1 of 2 arms at the time ofstudy entry. Both arms received imatinib 400 mg twicedaily for the first 6 months as a single agent. After 6months, patients randomized to Arm A continued therapywith single-agent imatinib 400 mg twice daily or at thesame dose they were receiving at the 6-month mark ifdose reductions were required during the first 6 months oftherapy. Those randomized to Arm B continued imatinib400 mg twice daily (or current dose at the 6-month mark)plus PEG IFN a-2b (Schering-Plough, Kenilworth, NJ)0.5 lg/kg subcutaneously weekly and GM-CSF (Berlex,Seattle, Wash) 125 lg/m2 3� per week. Hydroxyureaand/or anagrelide were allowed before and during the first6 weeks of therapy for white blood debulking.

Dose Modifications

Dose adjustments were done as per Table 1. An individualdrug could be discontinued in the event of excessive toxic-ity after appropriate dose reductions and management.Toxicities were evaluated using the National Cancer Insti-tute Common Terminology Criteria version 3.0. Drugswere dose-adjusted as follows (Table 1).

PEG IFN a-2b

For grade 3-4 nonhematologic toxicities, therapywas held until toxicity resolved to grade �1 and thenresumed with 1 dose level reduction; for persistent grade 2toxicity not responsive to supportive measures, therapywas reduced by 1 dose level.

Imatinib

For grade 2 nonhematologic toxicity unresponsiveto therapy, imatinib was withheld until resolution tograde �1 and then resumed at the same dose or at thenext lower dose level if the toxicity was recurrent; for grade3-4 toxicity, imatinib was withheld until resolution tograde �1 and then resumed at the next lower dose level.Imatinib was also held when the absolute neutrophilcount (ANC) was <0.5 � 109/L or platelets were <40 �109/L. Therapy was then resumed at the same dose level ifrecovery (granulocytes >1 � 109/L or platelets >60 �109/L) occurred within 2 weeks or at the next lower doselevel if this occurred beyond 2 weeks. The lowest andhighest imatinib dose allowed were 300 mg/d and 800mg/d. In patients with prior dose reductions, imatinibcould be dose-escalated if the patient remained free of tox-icity requiring dose adjustments for at least 1 month.Patients with dose reductions who did not achieve a mo-lecular remission 6 months after randomization and hadno toxicities could have their dose escalated back to 400mg twice daily.

Table 1. Dose Levels of Imatinib, PEG IFN a-2b,and GM-CSF Therapy

DoseLevel

PEG IFNa-2b,lg/kg/wk sc

GM-CSF,lg/kg sc tiw

Imatinib,Total DailyDose, mg

1 1 125 Monday-Friday NAa

0 0.5 125 800

�1 0.25 100 600

�2 0.125 50 400

�3 0.125 qow 50 biw 300

PEG indicates pegylated; IFN, interferon, GM-CSF, granulocyte-macro-

phage colony-stimulating factor; sc, subcutaneously; tiw, 3� per week; NA,

not applicable; qow, every other week; biw, 2� per week.aNo further imatinib dose escalation beyond 800 mg daily.

Pegylated-Interferon and Imatinib in CML/Cortes et al

Cancer February 1, 2011 573

GM-CSF

GM-CSF dose could be reduced by 1 dose level ifwhite blood cell (WBC) count was �20 � 109/L or esca-lated by 1 dose level if ANC was<0.5� 109/L. For grade3-4 nonhematologic toxicity related to GM-CSF, this wasdiscontinued until it resolved to grade 1 and then resumedat the next lower dose level.

Patient Evaluation

Before the start of study treatment, all patients had a com-plete history taken and received a complete physical exam-ination, a complete blood count (CBC), a comprehensivebiochemistry panel, a bone marrow (BM) aspirate withcytogenetics, and fluorescence in situ hybridization(FISH). A CBC with differential was obtained every 1 to2 weeks for 4 weeks, every 4 to 6 weeks for the first 12months of therapy, and every 3 to 4 months thereafter.Total bilirubin, alanine aminotransferase or aspartateaminotransferase, and creatinine were obtained every 2 to4 weeks for 1 month, then every 4 to 6 weeks for the first12 months of therapy, and every 3 to 4 months thereafter.BM aspirate and cytogenetics (FISH, when cytogeneticstudies were unevaluable) were performed every 3 to 4months for 1 year, then every 6 to 12 months during ther-apy. Real-time polymerase chain reaction (PCR) was per-formed every 3 for the first 12 months and every 6months thereafter. BM and/or peripheral blood sampleswith undetectable levels of BCR-ABL1 transcripts wereconfirmed by nested PCR as previously reported.5 Resultswere expressed according to the international scale (IS).Response criteria were as previously described.10 A majormolecular response was defined as a BCR-ABL1 IS tran-script levels of�0.1%, and a complete molecular responseas undetectable BCR-ABL1 transcript levels confirmed bynested PCR.

Statistical Considerations

An accrual of 98 patients was initially planned. Assumingrandomization of 92 patients and a 1-sided significancelevel of .05, the trial provided 80% power to detect a dou-bling in the rate of major molecular response. Patientswere assigned in a 1:1 ratio to Arms A and B. The studywas designed to be stopped before 98 patients wereaccrued if the probability of showing a significant benefitfor the combination arm (Arm B) over the high-dose ima-tinib arm (Arm A) was <5% or >95% by 12 months.The chi-square test and Fisher exact test were used to com-pare patient characteristics and response rates betweenboth treatment arms. Survival was estimated by the

Kaplan-Meier method and compared by the log-rank test.OS was calculated from the start of high-dose imatinib tothe date of death from any cause or last follow-up. Pro-gression-free survival (PFS) was calculated from the start ofhigh-dose imatinib to unsatisfactory response (similar tothe European Leukemia Net recommendations for defini-tion of failure), loss of complete cytogenetic response orCHR, progression to AP or blast phase, or death. For calcu-lation of EFS, events included failure to achieve major cyto-genetic response by 12 months, treatment discontinuationdue to toxicity, loss of CHR, loss of major cytogeneticresponse, increasing WBC count, death resulting from anycause, or progression to AP or blast phase.

RESULTS

Patient Characteristics

BetweenMay 2003 and July 2005, 94 patients with newlydiagnosed Philadelphia-positive chronic phase CML wererandomized to high-dose imatinib (Arm A; 49 patients)or to high-dose imatinib with PEG IFN a-2b and GM-CSF (Arm B; 45 patients) (Table 2). The median timefrom CML diagnosis to randomization was 25 days(range, 2-193 days). Fifteen (16%) patients had receivedtherapy with single-agent imatinib for a median of 16days (range, 7-30 days). Thirty-two (34%) patients werereceiving hydroxyurea or anagrelide but discontinuedwithin 7 days of study entry. The median follow-up for allpatients was 54 months (range, 7-70 months).

Response and Outcome

Ninety-one (97%) of 94 patients have been followed for�3 months. One patient in Arm A (lost to follow-up) and2 in Arm B (1 for noncompliance, 1 for treatment refusal)were taken off study before the 3-month first cytogeneticassessment. In addition, in Arm B, 11 (24%) patientswere noncompliant with PEG IFN a-2b. Table 3 summa-rizes the reported response rates. CHR was achieved in 89(95%) patients, whereas complete cytogenetic responseand partial cytogenetic response were attained in 82(90%) and 3 (3%) patients, respectively. Seventy-eight(91%) of 86 evaluable patients achieved major cytogeneticresponse at 12 months, including 76 (88%) with com-plete cytogenetic response. The rates of major cytogeneticresponse, complete cytogenetic response, and partial cyto-genetic response were 90%, 89%, and 1% at 24 months(82 patients evaluable) and 89%, 89%, and 0% at 30months (81 patients evaluable), respectively. Overall cyto-genetic responses by arm were as follows: 44 (92%) of 48

Original Article


patients assessable for response in Arm A achieved a majorcytogenetic response, including 43 (90%) with completecytogenetic response. In Arm B, 41 (95%) of 43 patientshad a major cytogenetic response, including 39 (91%)with a complete cytogenetic response (P¼ 1.0).

Figure 1 depicts the dynamics of molecularresponse. The median BCR-ABL1 IS transcript levels atthe time of randomization was 10.92 in Arm A and 10.62in Arm B (P ¼ .67). BCR-ABL1 IS transcript levelsdecreased at the same rate in both arms at 3 (0.26 vs 0.28)and 6 (0.025 vs 0.024) months. Although by 12 months atrend towards lower transcript levels was observed amongpatients in Arm B (0.017 vs 0.008) and maintained by 18months (0.011 vs 0.007), this was not confirmed at 24(0.0042 vs 0.0056) or at 30 (0.0028 vs 0.004) months.

Major molecular response was achieved by 44 (92%) of48 assessable patients in Arm A and by 36 (84%) of 43 inArm B (P ¼ .34). A complete molecular response wasobserved in 24 (50%) and 18 (42%) patients, respectively(P¼ .57).

Survival is shown in Figure 2A. Two patients inArm A died after 43 and 49 months of follow-up (graft-versus-host disease and Alzheimer disease, respectively)and 2 patients, receiving therapy in Arm B, died after 11and 26 months of follow-up (myocardial infarction andmelanoma, respectively). No significant differences in sur-vival were observed between arms (P ¼ .89). Figure 2Bdepicts the PFS. Five patients progressed in Arm A and 5in Arm B. There was no significant difference in PFSbetween the 2 arms (P ¼ .81). Likewise, no differences

Table 3. Cytogenetic and Molecular Responses for All 94 Patients Randomized to EitherHDIM (Arm A) or the Combination of HDIM, PEG IFN a-2b, and GM-CSF (Arm B)

Response Overalla HDIMa HDIM 1 PEG IFNa-2b 1 GM-CSFa

P

CG response at 12 monthsPartial 2/86 (2) 2/47 (4) 0/39 (0) .50

Complete 76/86 (88) 41/47 (87) 35/39 (90) 1.0

Best molecular response£0.1%b 80/91 (75) 44/48 (92) 36/43 (84) .34

Undetectable 42/91 (46) 24/48 (50) 18/43 (42) .57

Molecular response at 12 months£0.1%b 66/86 (77) 36/47 (77) 30/39 (77) 1.0

Undetectable 10/86 (12) 5/47 (11) 5/39 (13) 1.0

HDIM indicates high-dose imatinib; PEG, pegylated; IFN, interferon; GM-CSF, granulocyte-macrophage colony-

stimulating factor; CG, cytogenetic.a No./No. evaluable (%).b International scale.

Table 2. Patient Clinical Characteristics

Characteristic Overall Arm A, n 5 49 Arm B, n 5 45 P

Median age, y (range) 48 (19-79) 46 (19-73) 51 (19-79) .08

Median leukocyte count, �109/L (range) 26.9 (2.2-283) 29 (4.7-283) 25.4 (2.2-239) .39

Median hemoglobin level, g/dL (range) 12.4 (6.2-15.5) 12.5 (9-15.5) 12.4 (6.2-14.5) .53

Median platelet count, �109/L (range) 323 (58-1324) 316 (58-1324) 335 (107-998) .94

Median PB blasts, % (range) 0 (0-12) 0 (0-12) 0 (0-7) .15

Median PB basophils, % (range) 3 (0-16) 4 (0-13) 3 (0-16) .04

Median Philadelphia-positive metaphases, % (range) 100 (0-100) 100 (0-100) 100 (0-100) .42

Median PB BCR-ABL/ABL ratio, % (range) 78.04 (0.03-100) 78.04 (1.76-100) 75.92 (0.03-100) .63

Splenomegaly, No. 28 (30%) 18 (37%) 10 (22%) .18

Sokal scoreLow 65 (69%) 32 (65%) 33 (73%) .64

Intermediate 23 (24%) 13 (26%) 10 (22%)

High 6 (6%) 4 (8%) 2 (4%)

Prior imatinib therapy, No. 15 (16%) 7 (14%) 8 (18%) .78

PB indicates peripheral blood.



were observed between arms A and B regarding EFS (P ¼.97), even when treatment discontinuation was consid-ered an event (Fig. 2C).

Toxicity

The most frequent nonhematologic toxicities for the totalpopulation were fatigue (n¼ 79, 87%), periorbital edema(n ¼ 67, 74%), diarrhea (n ¼ 65, 71%), nausea (n ¼ 64,70%), and peripheral edema (n ¼ 61, 67%) (Table 4).Toxicities during the first 6 months of therapy were simi-lar to those reported in prior studies of high-dose imatiniband comparable between the 2 arms.2,3 In Arm A, high-dose imatinib-related toxicity declined significantly after6 months of therapy. Higher rates of fatigue (59%), fever(51%), influenza-like syndrome (36%), rash (31%),injection site reaction (31%), myalgia (28%), pruritus(28%), and depression (18%) were reported after theaddition of PEG IFN a-2b and GM-CSF in Arm B whencompared with Arm A. Grade 3-4 toxicities in Arm Bwere mainly fatigue (31%), headache (10%), and diarrhea(8%). Only 6 patients developed grade 3-4 toxicity inArm A, with the most frequent being peripheral edema(4%) and elevated liver enzymes (4%). After 6 months,significant differences were observed in the incidence ofneutropenia grade 3-4 (4% vs 12%), and thrombocytope-nia of any grade (8% vs 20%) between both arms.

Eleven (24%) and 12 (27%) of the 45 patientstreated in Arm B never started therapy with PEG IFN a-2b or GM-CSF, respectively. The main reasons were

Figure 2. Overall survival is shown for patients receiving ei-ther high-dose imatinib (HDIM) alone or HDIM, pegylated(PEG) interferon (IFN) a-2b, and granulocyte-macrophagecolony-stimulating factor (GM-CSF). (A) Kaplan-Meier esti-mates of the proportion of patients remaining alive, (B) theprobability of progression-free survival, and (C) event-freesurvival by treatment arm are shown.

Figure 1. Molecular response over time is shown for patientsreceiving either high-dose imatinib (Arm A, black curve) orhigh-dose imatinib, pegylated interferon a-2b, and granulo-cyte-macrophage colony-stimulating factor (Arm B, redcurve). Values are expressed according to the internationalstandard.

Original Article


patient’s refusal (n ¼ 5) or being taken off study beforethe start date (n ¼ 3). PEG IFN a-2b was eventually dis-continued in all 34 patients treated with this cytokine,due to influenzalike symptoms (n ¼ 5), fatigue (n ¼ 8),rash (n ¼ 4), myelosuppression (n ¼ 3), neurotoxicity(n ¼ 3), headache/pain (n ¼ 2), progression (n ¼ 2),death from cardiac event (n ¼ 1), increased liver functiontests (LFT) (n¼ 1), injection site reaction (n¼ 1), comor-bidities (n ¼ 1), or other personal reasons (n ¼ 3). GM-CSF was discontinued in all 33 patients treated with thisagent due to fatigue (n ¼ 8), rash (n ¼ 7), influenza-likesymptoms (n¼ 5), injection site reactions (n¼ 1), myelo-suppression (n ¼ 1), neurotoxicity (n ¼ 1), headache(n ¼ 1), progression (n ¼ 2), death from cardiac event(n¼ 1), increased LFT (n¼ 1), comorbidities (n¼ 1), orother personal reasons (n ¼ 4). Thirteen patients weretaken off study in Arm A due to imatinib resistance (n ¼3), increased transaminases (n¼ 2), renal insufficiency (n¼ 1), patient’s request (n ¼ 1), stem cell transplantation(n ¼ 2; 1 in complete cytogenetic response, 1 in partial

cytogenetic response), disease progression (n ¼ 1), deathof Alzheimer disease (n ¼ 1), or loss to follow-up (n ¼ 2).Thirteen patients in Arm B were taken off study because ofresistance (n ¼ 4), intolerance-rash (n ¼ 1), financial rea-sons (n ¼ 2), lack of compliance (n ¼ 2), increased LFT(n ¼ 1), metastatic melanoma (n ¼ 1), patient’s choice(n¼ 1), or death due tomyocardial infarction (n¼ 1).

Dose Intensity

Because toxicity precluded the administration of theplanned treatment in some patients, we determined theintensity of therapy delivered in both arms. The medianduration on high-dose imatinib in Arm A was 48 months(range, 1-68 months) and the median number of days offimatinib therapy was 7 (range, 0-200 days). The medianimatinib dose intensity in Arm A was 93% (range, 46%-100%). Twenty-five (51%) of 49 patients received 90%to 100% of the planned imatinib dose, 16 (33%) received70% to 89%, and 8 (16%) received 0% to 69%. Seven-teen (35%) of 49 patients had to reduce imatinib dose to

Table 4. Adverse Events Related to Therapy With HDIM (Arm A) and HDIM, PEG IFN a-2b, and GM-CSF (Arm B)

Toxicity No. (%) of Patients by Arm

Arm A Arm B Arm A 1 Arm BFirst 6 Months,

n549

After 6 Months,

n546

First 6 Months,

n545

After 6 Months,

n539

Overall, n594

Any

grade

Grade

3-4

Any

Grade

Grade

3-4

Any

Grade

Grade

3-4

Any

Grade

Grade

3-4

Any

Grade

Grade

3-4

HematologicAnemia 41 (45) 4 (4) 25 (27) 0 (0) 36 (40) 5 (5) 27 (30) 1 (1) 80 (88) 10 (11)

Thrombocytopenia 38 (42) 13 (14) 7 (8) 1 (1) 31 (34) 9 (10) 18 (20) 3 (3) 69 (76) 25 (27)

Neutropenia 32 (35) 15 (16) 25 (27) 4 (4) 27 (30) 11 (12) 19 (21) 11 (12) 66 (73) 36 (40)

NonhematologicFatigue 31 (63) 1 (2) 11 (24) 1 (2) 30 (67) 3 (6) 23 (59) 12 (31) 79 (87) 16 (18)

Periorbital edema 33 (67) 0 (0) 2 (4) 0 (0) 30 (67) 1 (2) 5 (13) 0 (0) 67 (74) 1 (1)

Diarrhea 24 (49) 1 (2) 14 (30) 0 (0) 26 (58) 0 (0) 19 (49) 3 (8) 65 (71) 4 (4)

Nausea 20 (41) 1 (2) 15 (33) 0 (0) 28 (62) 0 (0) 13 (33) 1 (3) 64 (70) 2 (2)

Peripheral edema 24 (49) 1 (2) 14 (30) 2 (4) 27 (60) 2 (4) 12 (31) 0 (0) 61 (67) 4 (4)

Cramps 17 (35) 1 (2) 10 (22) 0 (0) 24 (53) 0 (0) 9 (23) 1 (3) 53 (58) 2 (2)

Arthralgia 22 (45) 1 (2) 11 (24) 0 (0) 22 (49) 1 (2) 10 (26) 2 (5) 52 (57) 4 (4)

Fever 13 (27) 0 (0) 3 (7) 0 (0) 11 (24) 1 (2) 20 (51) 0 (0) 44 (48) 1 (1)

Myalgia 16 (33) 0 (0) 3 (7) 0 (0) 20 (44) 0 (0) 11 (28) 1 (3) 43 (47) 1 (1)

Headache 12 (24) 0 (0) 9 (20) 0 (0) 16 (36) 0 (0) 13 (33) 4 (10) 43 (47) 4 (4)

Pruritus 15 (31) 2 (4) 5 (11) 0 (0) 13 (29) 4 (8) 11 (28) 2 (5) 37 (41) 7 (8)

Rash 11 (22) 3 (6) 6 (13) 0 (0) 13 (29) 2 (4) 12 (31) 1 (3) 32 (35) 6 (7)

Dyspnea 6 (12) 0 (0) 8 (17) 1 (2) 8 (18) 1 (2) 11 (28) 1 (3) 29 (32) 3 (3)

Influenzalike syndrome 0 (0) 0 (0) 0 (0) 0 (0) 5 (11) 0 (0) 14 (36) 1 (3) 17 (19) 1 (1)

Elevated liver enzymes 4 (8) 0 (0) 4 (9) 2 (4) 2 (4) 0 (0) 5 (13) 2 (5) 14 (15) 4 (4)

Injection site reaction 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 12 (31) 0 (0) 12 (13) 0 (0)

Ocular hemorrhage 0 (0) 0 (0) 4 (9) 0 (0) 3 (7) 0 (0) 3 (8) 0 (0) 10 (11) 0 (0)

Depression 0 (0) 0 (0) 0 (0) 0 (0) 3 (7) 0 (0) 7 (18) 0 (0) 10 (11) 0 (0)

HDIM indicates high-dose imatinib; PEG, pegylated; IFN, interferon; GM-CSF, granulocyte-macrophage colony-stimulating factor.

Data represent the number of patients who developed any given toxicity in either arm of the study. Only the maximum grade was considered in the event of

recurrent toxicities.



�400 mg for a median of 392 days (range, 1-1347 days).In contrast, the median time on high-dose imatinibamong patients in Arm B was 44 months (range, 1-70months), and the median time off imatinib was 16 days(range, 0-306 days). Imatinib dose intensity in Arm B was92% (range, 45%-100%). Twenty-five (56%) of 45patients received 90% to 100% of the planned imatinibdose, 9 (20%) received 70% to 89%, and 11 (24%)received 0% to 69%. Twenty (44%) of 45 patients had toreduce the dose to 400 mg or lower for a median numberof 117 days (range, 2-1653 days).

The median time on PEG IFN a-2b therapy for the34 (76%) patients in Arm B who received this agent was335 days (range, 7-1191 days), the median time off PEGIFN a therapy 14 days (range, 0-118 days), and the me-dian time that PEG IFN a-2b had to be dose-reduced was38 days (range, 0-1105 days). Patients received GM-CSFfor a median time of 249 days (range, 1-1234 days), whichwas interrupted for a median of 10 days (range, 0-96days).

DISCUSSIONThe poor efficacy of imatinib in rendering complete mo-lecular response has been linked to the inherent resistanceof CML stem cells to tyrosine kinase inhibitors.21 Amathematical tetra-compartmental model postulates thatCML cells are hierarchically organized into leukemicstem cells (with limitless ability to self-renew), leukemicprogenitor cells (devoid of self-renewal capacity), differ-entiated leukemic cells (evolving toward specialized celltypes), and terminally differentiated cells.22 Imatinibinduces an initial dramatic decrease in BCR-ABL tran-scripts (5% per day), reflecting the rapid depletion ofmature differentiated and terminally differentiated cellsand a slower (0.8% per day) gradual turnover of leuke-mic progenitor cells.22 However, CML stem cells remainunaffected, in keeping with the observation that Philadel-phia-positive CD34þ cells, colony-forming cells, andlong-term culture-initiating cells can be readily isolatedeven after the achievement of complete cytogeneticresponse.23,24 BCR-ABL–expressing CD34þ/Lin� leuke-mic stem cells obtained from patients with CML inchronic phase remained quiescent but viable even in thepresence of growth factors and imatinib,8 providing a res-ervoir for the generation and expansion of imatinib-re-sistant mutant clones.25

The mechanism of action of IFN a involves restora-tion of the adhesion of leukemic stem cells to marrow

stroma, down-regulation of BCR-ABL expression, activa-tion of transcription factors that regulate cell prolifera-tion, maturation, and apoptosis,26-30 and generation ofdendritic cells that can present CML-specific antigens andenhance the immune recognition and elimination of leu-kemic cells.18 Importantly, IFN a has been recentlyshown to activate dormant hematopoietic stem cells byfacilitating their transition from a quiescent G0 phase toan active cell cycle state,31 whereas imatinib would act onmore differentiated leukemic cells, thus suggesting thatIFN a may sensitize (prime) CML cells to imatinib ther-apy. Therapy with imatinib 400 mg/d in combinationwith variable weekly doses of PEG IFN a-2b (50 lg, 100lg, or 150 lg) given to 76 patients with untreated chronicphase CML rendered major cytogenetic response andcomplete cytogenetic response rates of 83% and 70%,respectively, and 68% of patients with a complete cytoge-netic response also achieved major molecular response.32

Forty-five (59%) patients discontinued PEG IFN a-2btherapy, and the median administered dose ranged from32 lg to 36 lg weekly. The recently reported SPIRITstudy randomized patients with CML in early chronicphase to receive standard-dose imatinib, high-dose imati-nib (600 mg/d), imatinib þ cytarabine, or imatinib þPEG IFN a-2a.33 At 18 months, the PEG IFN a-2a–con-taining combination rendered the highest rate of majormolecular response (62%) compared with standard-dose(41%) or high-dose imatinib (52%), as well as the highestrate of BCR/ABL1 transcript levels (IS) �0.1% (36%)compared with 19% to 25% in the other arms.33 In thepresent study, however, no differences in major molecularresponse rates were observed on addition of PEG IFN a-2a to high-dose imatinib. Several differences between the2 studies could explain these discrepancies. First, in theSPIRIT trial, PEG IFN a-2a was initiated from the startof therapy, whereas in our study this was added after 6months of single-agent high-dose imatinib. Second, PEGIFN a-2a was used in the French study, whereas weemployed PEG IFN a-2b. Third, in our study, patientsreceived high-dose imatinib together with PEG IFN a-2b, whereas in the SPIRIT trial patients receiving thecombination used standard-dose imatinib. It is possiblethat when using high-dose imatinib, the addition of PEGIFN a may add little to the response rate. Finally, in ourstudy, GM-CSF was used in addition to PEG IFN a-2b.The possibility that the concomitant use of this growthfactor counteracted the potential benefit of interferonshould be entertained. However, it is still possible thatPEG IFN a-2b may prolong response duration, although

Original Article


such effect has not been seen in our study after a medianfollow-up of 54 months.

Several factors may have accounted for the nonsuper-iority of the combination arm. First, although the imatinibdose intensity between arms was virtually identical (93% vs92%), the overall treatment intensity in the combinationarm was significantly handicapped, because 11 (24%) of the45 patients did not start PEG IFN a-2b. Second, 32% ofpatients receiving PEG IFN a-2b discontinued therapywithin 12 months due to toxicity. Thus, only 23 (51%) of45 patients randomized to receive combination therapy at 6months were actually receiving PEG IFN a-2b at 12months. In the SPIRIT trial, 45% of patients have also dis-continued PEG IFN a-2a by 12 months.33 Third, treat-ment-related toxicity required the discontinuation of GM-CSF in 25 (56%) patients by 12 months. Thus, in allpatients randomized to Arm B, the intended treatmentapproach eventually failed as determined by the inability tocontinue the combination therapy (although most contin-ued imatinib as a single agent). However, analyzing onlythose patients who received �6 months of PEG IFN a-2b,we still did not observe a difference in response rate or long-term outcome (data not shown).

In summary, the combination of high-dose imatinibwith PEG IFN a-2b and GM-CSF has not impacted sig-nificantly the achievement of cytogenetic or major molec-ular response after 12 months of therapy at the doseschedule employed in the present study. The high drop-out rate observed in the combination arm due to toxicitymay have compromised any potential benefit from theproposed immune modulation. These results should beconsidered in the future design of more efficacious andtolerable therapies targeting minimal residual disease thatmay lead to the cure for CML.

CONFLICT OF INTEREST DISCLOSURESJorge Cortes received research support from BMS and Novartisand has served as consultant for BMS, and Hagop Kantarjianreceived research support from Novartis and BMS.

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immune modulation of minimal residual disease in early chronic phase chronic myelogenous leukemia :...

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