BELA trial update: Bosutinib (BOS) versus imatinib (IM) in patients (pts) with newly diagnosed chronic phase chronic myeloid leukemia (CP CML) after 30 months of follow-up.
6512 Background: The BELA study compared the efficacy and safety of BOS (dual Src/Abl kinase inhibitor) with IM in newly diagnosed CP CML. Methods: 502 pts with newly diagnosed CP CML were randomized to BOS 500 mg/d (n = 250) or IM 400 mg/d (n = 252) and stratified by Sokal risk group and geographic region. Efficacy analyses included all randomized pts (ITT); safety analyses included all treated pts (BOS, n = 248; IM, n = 251). Data described below are for ≥24 mo of follow-up; updated data for ≥30 mo of follow-up will be presented. Results: Median treatment duration was 27.5 mo in both cohorts; 63% of BOS pts and 71% of IM pts were still receiving treatment. The primary reason for BOS discontinuation was a treatment-emergent adverse event (TEAE; 24% vs 7% with IM); the primary reason for IM discontinuation was disease progression (13% vs 4% with BOS). Cumulative complete cytogenetic response (CCyR) rates by 24 mo were 79% for BOS and 80% for IM. Cumulative major molecular response (MMR) rates by 24 mo were 59% for BOS and 49% for IM (P = 0.019), including 16% and 12% of pts with complete molecular response (4.0-log sensitivity). On-treatment transformation to accelerated/blast phase occurred in 4 (2%) BOS pts and 13 (5%) IM pts. Deaths were reported for 7 BOS pts (6 due to CML progression) and 13 IM pts (10 due to CML progression); 24-mo Kaplan-Meier overall survival estimates were 97% (BOS) and 95% (IM). BOS was associated with higher incidences of gastrointestinal events than IM (diarrhea [70% vs 25%], vomiting [32% vs 16%]; primarily transient), but lower incidences of edema (13% vs 40%) and musculoskeletal events (cramps [4% vs 22%], bone pain [4% vs 10%]). Grade ≥3 TEAEs in ≥2% of BOS or IM pts were diarrhea (12% vs 1%), vomiting (3% vs 0%), and rash (2% vs 1%). Grade ≥3 lab abnormalities (≥15% of pts) with BOS and IM were neutropenia (10% vs 24%), thrombocytopenia (14% vs 15%), elevated alanine aminotransferase (23% vs 4%), and hypophosphatemia (6% vs 20%). Conclusions: BOS was effective for newly diagnosed CP CML and had a distinct toxicity profile. With continued follow-up both on-treatment transformation to accelerated/blast phase and overall survival continue to favor BOS versus IM.