Published online 6 October 2008
Haematologica, Vol 93, Issue 12, 1792-1796 doi:10.3324/haematol.13068
Copyright © 2008 by Ferrata Storti Foundation
Chronic myeloid leukemia in blast crisis treated with imatinib 600 mg: outcome of the patients alive after a 6-year follow-up
Francesca Palandri1,
Fausto Castagnetti1,
Nicoletta Testoni1,
Simona Luatti1,
Giulia Marzocchi1,
Simona Bassi2,
Massimo Breccia3,
Giuliana Alimena3,
Ester Pungolino4,
Giovanna Rege-Cambrin5,
Riccardo Varaldo6,
Maurizio Miglino6,
Giorgina Specchia7,
Eliana Zuffa8,
Felicetto Ferrara9,
Monica Bocchia10,
Giuseppe Saglio5,
Fabrizio Pane11,
Daniele Alberti12,
Giovanni Martinelli1,
Michele Baccarani1,
Gianantonio Rosti1 on behalf of the GIMEMA Working Party on Chronic Myeloid Leukemia
1 Department of Hematology/Oncology "L. and A. Seràgnoli" S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
2 Division of Hematology, AIEOP, Milano, Italy
3 Department of Cellular Biotechnology and Hematology, University "La Sapienza", Rome, Italy
4 Division of Hematology, Ospedale Niguarda, Milano, Italy
5 Department of Clinical and Biological Science, University of Turin at Orbassano, Torino, Italy
6 Division of Hematology, San Martino Hospital, Genova, Italy
7 Division of Hematology, Bari, Italy
8 Division of Hematology, Ravenna, Italy
9 Division of Hematology, Napoli, Italy
10 Hematology Section, University of Perugia, Italy
11 CEINGE Biotecnologie Avanzate and Department of Biochemistry and Medical Biotechnology, University of Naples Federico II, Napoli, Italy
12 Novartis Pharmaceutical, East Hanover, NJ, USA
Correspondence: Gianantonio Rosti, Institute of Hematology and Medical Oncology "L. and A. Seràgnoli", S. Orsola-Malpighi University Hospital, via Massarenti, 9 40138 Bologna, Italy. E-mail:gianantonio.rosti{at}unibo.it

ABSTRACT
Background: Imatinib mesylate is the first line treatment for chronic myeloid
leukemia. In patients with advanced phase of the disease, the
advent of imatinib significantly increased survival. However,
few long-term data, based on large, prospective and controlled
trials are available on the outcome of these patients.
Design and Methods: We conducted a phase II trial of imatinib 600 mg daily in patients with chronic myeloid leukemia in blast crisis. The return to chronic phase was defined as <15% blasts and <30% blasts plus promyelocytes in blood or bone marrow and <20% peripheral basophils. A complete hematologic response required the normalization of platelet and white cell differential counts and absence of extramedullary involvement. Cytogenetic response was assessed by the standard banding technique and rated as usual.
Results: Ninety-two patients were enrolled (20 with lymphoid blast crisis and 72 with myeloid blast crisis). Forty-six patients (50%) returned to chronic phase, and 24 patients (26%) achieved also a complete hematologic response. Sixteen patients (17%) had a cytogenetic response (9 complete, 1 partial, and 6 minor or minimal). The complete cytogenetic response was subsequently lost by all but two patients between 2 and 12 months after first having achieved it: the median duration of complete cytogenetic response was 7 months. All responses were sustained for a minimum of 4 weeks. The median survival of all the patients was 7 months. After a median observation time of 66 months, seven (8%) patients are alive. Three of these patients are on imatinib treatment (1 in complete hematologic remission, 1 in partial cytogenetic response and 1 in complete cytogenetic remission). Three patients are in complete remission after allogeneic stem cell transplantation. One patient is alive in blast crisis, on therapy with a second-generation tyrosine kinase inhibitor.
Conclusions: Imatinib was effective and safe in the short-term treatment of chronic myeloid leukemia in blast crisis, but longer-term outcome was not significantly influenced (ClinicalTrials.gov identifier: NCT00514969).
Key words: chronic myeloid leukemia, blast crisis, imatinib, outcome, long-term.

Introduction
Blast crisis (BC) is the terminal phase of chronic myeloid leukemia
(CML), a clonal myeloproliferative disease characterized by
a reciprocal t(9;22)(q34;q11) chromosomal translocation, which
creates the Philadelphia chromosome (Ph) and leads to the expression
of the BCR-ABL fusion protein, whose deregulated constitutive
tyrosine kinase activity is responsible for leukemogenesis.
In more than 95% of the patients, blast crisis is preceded by
an initial period of chronic phase CML. While
BCR-ABL gene expression
is sufficient to promote the chronic phase phenotype, progression
to blast crisis depends on genomic instability, with accumulation
of additional genetic changes, which leads to loss of differentiation
and to a more aggressive clinical presentation. Treatment of
BC-CML with chemotherapy regimens inherited from therapeutic
experience in acute leukemias, produces only temporary benefits,
if any.
1,2 Allogeneic stem cell transplantation induces a durable
remission in less than 10% of patients, with overall survival
at 2 years ranging from 16% to 22%.
3
In 2000, the introduction of imatinib mesylate (Glivec; Novartis Pharmaceuticals, NJ, USA), a small molecule that selectively inhibits the BCR-ABL tyrosine kinase, provided a new option for the treatment of BC-CML.4 In the light of the favorable results of the phase I/II studies on imatinib, in 2001 the Italian Cooperative Study Group on CML (now GIMEMA Working Party on CML) conducted a phase II trial to confirm the activity and safety of imatinib 600 mg in the treatment of BC-CML. The reported 6-year follow-up is the longest in this setting of patients. This cohort of patients is consequently a valuable source of data for the assessment of the very long-term compliance to and efficacy of imatinib therapy, covering response duration and survival, and for the characterization of the prognostic factors associated with a favorable outcome.

Design and Methods
Patients
From June 2000 to April 2001, 92 patients with confirmed Ph-positive
BC-CML were enrolled into a prospective study (CML/003/STI571)
which was designed, sponsored and carried out by the Italian
Cooperative Study Group on CML according to good clinical practice
and the principles of the Helsinki declaration. Informed consent
was obtained from the participants according to institutional
guidelines. The primary end-point of the study was to determine
the rate of sustained hematologic responses in adult patients
with Ph-positive CML in accelerated and blast phase; the secondary
end-point was the assessment of the duration of hematologic
and cytogenetic responses and overall survival, and the safety
of the study drug. To be eligible, patients had to (i) have
morphologic and cytogenetic evidence of Ph-positive BC-CML;
(ii) be 18 years or older; (iii) have an adequate performance
status (level 0 to 2 on the World Health Organization Scale);
(iv) have normal renal function; and (v) normal hepatic function.
Exclusion criteria included: (i) childbearing potential wihout
a negative pregnancy test prior to initiation of the treatment;
(ii) previous treatment with antileukemic agents, if sufficient
time had not elapsed for potential recovery of the nadir in
blood counts to have occurred; (iii) grade 3/4 cardiac disease;
(iv) a history of non-compliance to medical regimens or patients
considered potentially unreliable. All patients were naïve
to imatinib treatment, and represented an estimated 50% of all
the new cases of CML in blast crisis diagnosed in Italy in this
period.
Chromosome banding analysis was used to confirm the presence of Ph-positive metaphases and to identify other chromosomal abnormalities. Blast crisis was defined as the presence of 30% blasts in blood or marrow and/or the presence of extramedullary disease (other than liver or spleen enlargement). The definition of the myeloid or lymphoid phenotype was confirmed by flow cytometry. Imatinib was given at a starting dose of 600 mg daily. Treatment was continued until disease refractoriness or progression, death, or treatment failure from other causes.
Response definitions and statistics
The return to chronic phase was defined as less than 15% blasts and less than 30% blasts plus promyelocytes in blood or bone marrow and less than 20% peripheral basophils. A complete hematologic response required the normalization of platelet and white cell differential counts and the absence of extramedullary involvement. The cytogenetic response was assessed by chromosome banding analysis prior to treatment and at 1–3 month intervals thereafter, and rated as described elsewhere.5 Hematologic and cytogenetic responses needed confirmation after a minimum period of 4 weeks (sustained responses). Survival analysis was based on the Kaplan-Meier method.6 Differences among groups were compared by the log-rank test.7 Comparison of frequencies were calculated with the
2 test or the Fishers exact test, as appropriate.

Results
Patients characteristics
The pre-treatment characteristics of the 92 patients are listed
in
Table 1. The median age at the start of imatinib was 55 years
(range 18–88); 59 patients (64%) were male and 33 female.
Twenty-seven out of the 92 (29%) patients had received intensive
chemotherapy prior to imatinib; eight patients presented evidence
of extramedullary disease and 36 (39%) had a performance status
of 2. Clonal evolution with additional chromosomal aberrations
was observed in 20 patients (22%), including trisomy 8 (1 patient),
a second Ph chromosome (2 patients), isochromosome 17 (1 patient),
deletion 9 (1 patient), and single additional alterations (4
patients). Variant translocations were discovered in one case
and ten patients had a complex karyotype with at least three
additional chromosomal aberrations (4 of whom carried trisomy
8).
Safety
Non-hematologic grade 3–4 side effects included nausea and vomiting (3%), liver dysfunction (6%), skin rash (4%) and fluid retention and edema (9%). Hematologic reactions were difficult to separate from the pre-treatment degree of myelosuppression: febrile episodes due to grade 3–4 neutropenia were recorded in 13 patients (17%), 30 patients required platelet transfusions and one patient died because of cerebral hemorrhage, while severely thrombocytopenic.
Efficacy
All 92 patients were included in the efficacy analysis. Eighteen (20%) patients were previously untreated; 57 (62%) patients had received therapy with interferon-
, hydroxyurea and/or cytarabine, whereas 27 (29%) patients had previously received intensive chemotherapy (including conventional induction chemotherapy, autologous and/or allogeneic stem cell transplantation). Table 2 shows a summary of the hematologic and cytogenetic responses of all 92 patients and after stratification according to prior treatment. Forty-six patients (50%) returned to chronic phase, and 24 patients (26%) also achieved a complete hematologic remission. Responses usually occurred early after the start of treatment: of the 46 patients with a return to chronic phase, 31 (68%) achieved their first response within 1 month of imatinib therapy. The return to chronic phase was subsequently lost by 22 patients, for a median duration of the second chronic phase of 11 months (range, 1–67). Sixteen patients lost the complete hematologic response, for a median duration of the hematologic response of 6 months (range 1–43). Sixteen patients (17%) had a cytogenetic response (9 complete, 1 partial, and 6 minor or minimal). The median time to complete cytogenetic response was 3 months (range, 1–11 months). The complete cytogenetic response was subsequently lost by all but two patients between 2 to 12 months after it had first been achieved, for a median complete hematologic response duration of 7 months. No patient underwent dose escalation to 800 mg.
Survival
Overall survival for the entire group and patients divided according
to the type of blast crisis (myeloid, 72 patients; lymphoid,
20 patients) is shown in
Figure 1A. The Kaplan-Meier
5 median
survival time was 7 months, and the survival rates were 53%
at 6 months (95% CI, 43%–63%), 29% at 12 months (95% CI,
19%–39%), 23% at 18 months (95% CI, 14% to 33%) and 11%
at 36 months (95% CI, 4%–18%). There were no differences
in terms of survival between patients in myeloid or lymphoid
blast crisis (
p=0.4); however, the number of patients with lymphoid
blast crisis was small (n=20). Eighty-five patients (92%) have
died: 78 (92%) because of BC-CML after 0.5 to 58 months of imatinib
treatment (median, 6 months), 6 patients from complications
after allografting and 1 patient while in chronic phase (myocardial
infarction). Nine patients underwent allogeneic stem cell transplantation:
eight patients in blast crisis, after 1 to 37 months of imatinib
therapy (median, 2.5 months) and one patient after 3 years of
continuous complete cytogenetic remission. The other patients
were not submitted to allogeneic transplantation because of
fully active disease (56 patients), age older than 60 (14 patients),
or unavailability of a donor (13 patients). At a median observation
time of 66 months, seven (8%) patients are alive: three patients
are still on treatment with imatinib at the scheduled dose (1
in complete hematologic remission, 1 in partial cytogenetic
remission and 1 in complete cytogenetic remission). Three patients
are in complete remission after allogeneic stem cell transplantation.
One patient is alive in blast crisis, on therapy with a second-generation
tyrosine kinase inhibitor, initiated because of loss of the
hematologic response 51 months after the start of imatinib therapy.
Univariate (log-rank) analyses
7 were used to test for the effects
of several baseline variables on survival. Results of those
log-rank analyses indicated that a lower percentage of peripheral
blasts (<50%) and better performance status (<2) were
associated with prolonged survival. As expected, patients who
achieved a hematologic response or a major cytogenetic response
benefited most from imatinib therapy. The median survival time
for the 46 patients achieving a hematologic response was 12
months (
vs. 5 months in patients without any hematologic response,
p=0.0001,
Figure 1B), whereas the median survival was 20.5 months
for the ten patients who achieved a major cytogenetic response
and 6 months for patients without such a response (
p=0.001,
Figure 1C).

Discussion
Imatinib was first tested for the treatment of CML in advanced
phase 8 years ago, to determine whether this drug could induce
higher rates of hematologic and cytogenetic responses than those
induced by conventional chemotherapy. The reported outcome of
these patients, treated with imatinib alone at variable doses,
showed an incidence of hematologic improvement ranging from
52% to 62%, with 16% to 30% of patients obtaining a complete
hematologic response and 3% to 16% of the patients also achieving
a major cytogenetic response,
8–11 with a median survival
ranging from 6 to 7.5 months.
We report the long-term outcome of 92 BC-CML patients homogeneously treated with imatinib 600 mg/daily. Response rates were comparable to those reported in the literature, with 50% and 12% of the patients obtaining a hematologic or major cytogenetic response, respectively. Among the baseline characteristics tested for association with survival, only better performance status (<2) and lower peripheral blast count (<50%) had significant impacts on survival in multivariate analysis, probably reflecting the severity of the disease. Imatinib treatment in this setting of patients was associated with several adverse events, as expected, because BC-CML is burdened by a considerable morbidity. Non-hematologic side-effects were, however, generally mild and manageable with temporary dose-reductions; no treatment-related deaths occurred. However, after a median follow-up of more than 5 years, only 7% of the study population were still alive, with 3% of the patients continuing imatinib therapy at the scheduled dose, without toxicity.
Since 2001, the mechanisms of resistance to imatinib have been at least partially elucidated5,12,13 and many studies are ongoing, investigating combinations of imatinib with other drugs14–17 and the role of second-generation tyrosine kinase inhibitors.18–21 Unfortunately, we have no data on the mutational status of BCR-ABL before and during imatinib therapy, which might have shed some light on the causes of primary and secondary resistance, since this study accrued patients at a time when mutational status was still highly experimental and not available in most of the molecular biology laboratories collaborating with the Italian Cooperative Study Group. This final analysis of a multicenter experience confirms that imatinib as monotherapy provides hematologic control in BC-CML with an acceptable level of toxicity. However, the relapse rate was high and the longer term clinical outcome was not significantly influenced, comparing the present results (median and long-term survival) with previous results obtained with conventional chemotherapy. Further studies are warranted to investigate induction treatment of BC-CML based on combination therapy or sequential use of second-generation tyrosine kinase inhibitors with other agents, and to explore new strategies for patients who initially respond but do not have a suitable donor for transplantation.

Acknowledgments
the skilful assistance of Katia Vecchi is gratefully acknowledged.

Footnotes
Authorship and Disclosures
FP: collected data and wrote the manuscript; MB, GR: designed and supervised the study and gave final approval of the manuscript; FC, NT, SB, AML, MM, MB, EP, RV, GS, GR-C, EZ, FF, MB, GS, FP, GM: contributed to the development of the study and to data collection. GR-C: speaker bureau Novartis and Bristol Myers Squibb; FP: research grant from Novartis, honoraria from Novartis, Bristol Myers Squibb and Roche; GS: advisory board and speaker bureau Novartis and Bristol Myers Squibb, research grant from Novartis; GR: grant and speaker bureau (Novartis), speaker bureau (Bristol Myers Squibb); MB: research grants and honoraria as speaker and consultant from Novartis Pharma. DA is an employee of Novartis.
Funding: this study was supported by the Italian Association for Cancer Research (A.I.R.C.), by Fondazione del Monte di Bologna e Ravenna, by European LeukemiaNet funds and by BolognAIL.
Received for publication March 13, 2008.
Revision received August 13, 2008.
Accepted for publication August 14, 2008.

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