Bosutinib May Be Effective As First-Line Therapy in Chronic-Phase Chronic Myeloid Leukemia

CHICAGO—Bosutinib may lead to improved 2-year major molecular response (MMR) among patients with newly diagnosed chronic phase chronic myeloid leukemia (CP-CML) compared with imatinib, according to a presentation at the American Society of Clinical Oncology 2018 Annual Meeting on Saturday, June 2.¹

The ongoing phase 3 BFORE study (ClinicalTrials.gov Identifier: NCT02130557) assessed the efficacy of first-line bosutinib 400 mg once daily — a dual Src/Abl tyrosine kinase inhibitor approved for newly diagnosed CP-CML and relapsed/refractory CML — versus imatinib 400 mg once daily. Researchers randomly assigned 536 patients to bosutinib or imatinib treatment arms, with a planned follow-up period of 5 years. The authors presented findings from the 24-month follow up.

Results showed that patients treated with bosutinib had a higher MMR compared with imatinib after 12 months (46.6% vs 37.0%; P = .013). This effect persisted after 18 months (57.0% vs 47%; P = .0198), and even after 24 months (61.2% vs 50.7%; P = .015). The cumulative complete cytogenetic response rate (CCyR) was improved among patients in the bosutinib arm compared with imatinib at both 48 weeks (78% vs 66%, respectively) and 96 weeks (82% vs 76%, respectively).

The cumulative incidence of MR⁴ in the bosutinib arm was 17% versus 10% in the imatinib arm after 48 weeks and was 34% versus 27% after 96 weeks (P = .0249). The cumulative incidence of MR^4.5 in the bosutinib arm was 6% versus 3% in the imatinib arm after 48 weeks, and was 20% versus 15% after 96 weeks (P = .0542).

The time to MMR and CCyR were longer in the imatinib arm compared with bosutinib at 24 months, which were consistent with findings reported at 12 months. There were 6 and 7 transformations to accelerated and blast phase CML among patients in the bosutinib and imatinib arms, respectively.

Seventy-one percent of patients remained on bosutinib therapy after 24 months, and 66% of patients remained on imatinib therapy.

Both study arms reported encouraging rates of overall survival, with 99.6% and 98.1% at 12 months in the bosutinib and imatinib arms, respectively, and 99.2% and 97.0% at 24 months, respectively.

The authors concluded that “at 24 [months], a higher MMR rate was maintained with bosutinib vs imatinib. The results support the use of bosutinib as first-line therapy for CP-CML.”

Read more of Cancer Therapy Advisor‘s coverage of the American Society of Clinical Oncology (ASCO) 2018 meeting by visiting the conference page.

Reference

1. Cortes JE, Mauro MJ, Deininger MWN, et al. Bosutinib vs imatinib for newly diagnosed chronic myeloid leukemia in the BFORE trial: 24-month follow-up. Oral presentation at: 2018 ASCO Annual Meeting; June 1-5, 2018; Chicago, IL.