Disease Patterns for Patients (pts) with Chronic Myeloid Leukemia (CML) That Have BCR-ABL Transcript Levels > 10% At 3 Month of Therapy with Tyrosine Kinase Inhibitors (TKIs)

Response to TKIs in CML at 3 month is a strong predictor for long term outcome in CML patients treated with TKIs. Pts who do not achieve a BCR-ABL transcript level < 10% or a MCyR at 3 months have lower event-free survival (EFS) and perhaps overall survival (OS). However, pts have rarely changed therapy based on response at this early time points. The purpose of this analysis is to understand the patterns of disease progression and management in this group of patients.

A total of 489 newly diagnosed CML pts that received initial treatment with TKIs: imatinib 400 mg daily (83) imatinib 800 mg daily (199), and second generation TKIs (2GTKIs) (207) in consecutive or parallel trials between 7/2000 and 6/2011 were included in this analysis. Cytogentic and molecular responses were evaluated every 3 month for the first year and then every 6 month. Event was defined as transformation to accelerated phase (AP) or blast phase (BP), loss of complete hematologic response (CHR), or loss of MCyR.

Among the 489 treated pts, 58 (12%) did not achieve a MCyR or BCR-ABL transcript level < 10 % at 3 months (26 pts (31%) received IM400, 19 (10%) IM800, and 13 (6%) 2GTKIs. Eleven of these pts (19%) had high sokal score at diagnosis (1 pt treated with imatinib 400, 7 with imatinib 800, 3 with 2GTKIs). By 6 months, 52/58 pts (90%) continued on their original therapy: 39 (67%) at the same dose and 19 (33%) with a decreased dose because of adverse events. No pt had a dose increase. Six pts had discontinued therapy by 6 month: 4 due to intolerance, 1 loss of CHR and 1 for progression to BP. At 6 month, 27 pts (47%) achieved MCyR or BCR-ABL transcript level < 10 %. At 12 months, 47 pts (81%) were still receiving their initial therapy, 11 pts (19%) had discontinued their initial TKI: 6 due to intolerance, 1 loss of CHR, 2 for progression to BP, and 2 for resistant disease. After a median follow up of 95 months, 17 pts (29%) continue to receive their initial therapy and their current disease status are: complete cytogenetic response (CCyR) in 14 (82%), 2 (12%) lost their CCyR, and 1(6%) pt who never achieve any cytogenetic or molecular response and remains in chronic phase on the same dose of imatinib for over 8 years. Among these 17 pts, 11 (65%) have MMR, 2 (12%) with MR^4.5, and 4 (24%) have lost MMR (2 of them with loss of CCyR). The 5 years OS, EFS and transformation-free survival (TFS) for the patients who did not achieve any response at 3 month was 88%, 77%, and 94%, respectively. The OS, EFS, and TFS for the patients who subsequently achieved a response (MCyR or BCR-ABL transcript level < 10 %) at 6 month was 100%, 66%, and 95%, respectively vs those who continued to have no response 79%, 95%, and 100%, respectively (P = 0.17, 0.07, 0.99, respectively).

Although BCR-ABL transcript level at 3 month may predict long-term outcome of pts with CML treated with TKIs, this represents a static, one-time measure. Assessing the response at 6 months of pts with poor response at 3 months may provide a better predictor of long term outcome.

Cortes:Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Ariad: Consultancy, Research Funding.