Promising Outcome of Imatinib-Combined Chemotherapy Followed by Allogeneic Hematopoietic Stem Cell Transplantation for Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: Results of the Japan Adult Leukemia Study Group (JALSG) Ph+ALL202 Regimen.

Abstract 3090

Poster Board III-27

The outcome of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) has dramatically improved since the start of treatment with imatinib. The Japan Adult Leukemia Study Group (JALSG) has reported a high complete remission (CR) rate for Ph+ALL treated with imatinib-combined chemotherapy (Yanada et al, J Clin Oncol 2006). Here we report a follow-up analysis of the results of the JALSG imatinib-combined chemotherapy. In the study, remission was induced by administering imatinib from day 8 to day 62 in combination with cyclophosphamide, daunorubicin, vincristine (VCR), and prednisolone (PSL). Consolidation regimen consisted of an odd course comprising high-dose methotrexate and high-dose cytarabine and an even course with 28 days administration of single-agent imatinib. The consolidation regimens were alternated for four courses each. Maintenance consisting of VCR, PSL, and imatinib was continued for two years after a CR. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) was recommended if HLA identical sibling donor was available and was allowed from an alternative donor.

A total of 103 newly diagnosed Ph+ALL patients were enrolled in the study between August 2002 and August 2004. Median age of the patients was 45 years (range, 15-64 years), and there were 57 males and 46 females. Median follow-up period was 2.6 years (range, 0.1-5.1 years). A CR was achieved in 100 (97.1%) of the 103 patients and not achieved in a patient in whom imatinib was discontinued because of ileus. There were two early deaths during induction.

The probability of overall survival (OS) rate for the entire group at three years was 56.8%. No severe adverse effects were observed. Allo-HSCT was performed in the 1st CR (CR1) in 54 of the 74 CR patients under 55 years of age. Relapse occurred in 18 of 20 patients (90.0%) in whom allo-HSCT was not performed in CR1, but in only seven of the 54 patients (13.0%) who underwent allo-HSCT. At three years, the probability of OS rate for patients under 55 years of age was 75.0% in the transplanted group and 36.4% in the non-transplanted group. Allo-HSCT was performed in CR1 in eight of the 25 patients over 55 years of age. Two were myeloablative and six reduced intensity conditionings. Seven of eight patients who underwent HSCT are still alive in a CR. However, the probability of OS rate at three years in the non-transplanted group was 43.2%.

In the group that did not receive allo-HSCT in CR1, age (55< years or 55> years), WBC count, bcr/abl transcript level, bcr/abl transcript type (major or minor), co-expression of myeloid antigens (CD13 and/or CD33), and additional chromosomal abnormalities at diagnosis were not associated with OS.

The results demonstrated that the imatinib-combined chemotherapy regimen was effective and feasible. The regimen provided a better chance to receive allo-HSCT which resulted in an excellent outcome. However, relapse still remains a problem, especially in patients who are not candidates for allo-HSCT.