Seven-Year (yr) Follow-up of Patients (pts) with Imatinib-Resistant or -Intolerant Chronic-Phase Chronic Myeloid Leukemia (CML-CP) Receiving Dasatinib in Study CA180-034, Final Study Results

Background: Dasatinib is a potent BCR-ABL tyrosine kinase inhibitor (TKI) currently approved at 100 mg once daily (QD) as a first-line therapy in CML-CP pts and a second-line therapy in pts with CML resistant/intolerant to prior therapy. CA180-034 (NCT00123474), a prospective, randomized phase 3 study, was designed to compare the dose and schedule of dasatinib therapy for the optimal benefit/risk ratio among pts with imatinib-resistant or -intolerant CML-CP. Results from this study have previously demonstrated significant efficacy of dasatinib in this pt population. Here, we report the final 7-yr analysis of efficacy and safety outcomes of CA180-034, which represents the longest follow-up of any second-generation BCR-ABL TKI to date.

Methods: The CA180-034 2 X 2 factorial study design has previously been described (Shah 2010, J Clin Oncol). Pts (n=670) were randomized to dasatinib: 100 mg QD (n=167), 50 mg twice daily (BID; n=168), 140 mg QD (n=167), or 70 mg BID (n=168). To manage inadequate response or adverse events (AEs), dose escalation (up to a total daily dose [TDD] of 180 mg) and dose interruption or reduction (down to a TDD of 20 mg) were allowed. After 2 yrs, the protocol was amended to allow switching to a QD regimen with the same TDD after at least one dose reduction for recurrent anemia, thrombocytopenia, neutropenia, pleural effusion, or any other fluid retention during study progress or at the investigator’s discretion (Shah 2014, Blood).

Results: Approximately 55% (50 mg BID) and 51% (70 mg BID) of pts treated after the protocol amendment switched to QD dosing by the last recorded dose. The overall median duration of therapy was longer for the 100 mg QD group (37.4 months [mos]) compared with the 50 mg BID, 140 mg QD, and 70 mg BID groups (28.1 mos, 26.6 mos, and 28.9 mos, respectively).At 7 yrs of follow-up, progression-free survival (PFS) andoverall survival (OS) rates were similar for all doses, as were the proportions of pts with a best on-study molecular response of MMR (Table 1). In an exploratory landmark analysis, pts in the 100 mg QD arm with BCR-ABL ≤10% (on the International Scale) at 3 mos had improved PFS and OS rates at 7 yrs relative to pts with BCR-ABL>10% (Table 2). BCR-ABL mutations were assessed in pts prior to the start of dasatinib (baseline), at the time of disease progression, or at end of treatment. Three mutations persisted or developed in pts who discontinued dasatinib due to loss of response on 100 mg QD: V299L (n=3), T315I (n=6), and F317L (n=7). For 100 mg QD, most nonhematologic and hematologic AEs (all grades) typically first occurred within the first 24 mos of treatment. Rates of nonhematologic AEs (all grades) over 7 yrs for 100 mg QD compared with other treatment arms included fluid retention (51% vs 54%), diarrhea (42% vs 47%), nausea/vomiting (27% vs 43%), myalgias/arthralgias (38% vs 33%), fatigue (37% vs 34%), and rash (33% vs 36%). Within yr 7 of the study, new cases of pleural effusion occurred in 5% (2/42) of pts at risk treated with dasatinib 100 mg QD compared with 8% (7/88) in other treatment arms. Severe (grade 3–4) AEs (any relationship) occurred less frequently in the 100 mg QD group (98/165, 59%) relative to other treatment arms (341/497, 69%). Three pts died due to study drug toxicity (1 due to sepsis; 1 due to pulmonary edema, congestive heart failure, neck pain, and pleural effusion; 1 due to necrosis of the colon).

Conclusions: Long-term follow-up of dasatinib continues to demonstrate durable efficacy and benefit for pts with CML-CP following imatinib therapy, particularly if achieving BCR-ABL ≤10% at 3 mos. Dasatinib is well-tolerated amongst pts, with most AEs occurring early on during the course of treatment; however, pleural effusion did occur through 7 yrs of treatment. No new safety signals were detected.