BFORE: Bosutinib remains superior to imatinib in CML at 2 years
Use of bosutinib in the treatment of chronic myeloid leukaemia (CML) still proves to be more effective than imatinib, with a higher major molecular response (MMR) rate, according to the 24-month follow-up data from the phase III BFORE* trial.
“The results continue to support the use of bosutinib as first-line therapy for chronic-phase CML,” researchers said.
In the current 24-month analysis, 536 patients (intent-to-treat population; median age 53 years; 58 percent male) with chronic-phase CML were randomized to treatment with bosutinib (n=268) or imatinib (n=268). Patient distribution was similar between the treatment arms for Sokal scores: high-risk (39 percent vs 40 percent), intermediate-risk (41 percent for both) and low-risk (20 percent for both).
The primary endpoint of MMR at 24 months was markedly higher with bosutinib than with imatinib (61.2 percent vs 50.7 percent; p=0.0146), consistent with findings at 12 months (46.6 percent vs 36.2 percent; p=0.0126) and 18 months (56.7 percent vs 46.6 percent; p=0.0198). [EHA 2018, abstract PF369]
However, the between-group difference in rates of deeper molecular responses (MRs) were smaller (MR4, 32.8 percent with bosutinib vs 25.4 percent with imatinib; p=0.73; MR4.5, 13.1 percent vs 10.8 percent, respectively; p=0.428).
Of note, MMR (hazard ratio [HR], 1.37; p=0.004), complete cytogenetic response (CCyR; HR, 1.34; p=0.005), MR4 (HR, 1.39; p=0.025) and MR4.5 (HR, 1.42; p=0.054) occurred more rapidly in the bosutinib group than in the imatinib group, consistent with 12-month data.
There were 14 patients in the bosutinib group and 17 in the imatinib who had on-treatment events, including death (n=1 and 4, respectively), transformation to accelerated/blast phase (n=6 and 7), loss of CCyR (n=3 and 5), loss of complete haematologic response (CHR; n=1 and 3), and doubling of white blood cell count for patients without CHR (n=4 and 0).
After ≥24 months, 71 percent and 66 percent of bosutinib- and imatinib-treated patients, respectively, remained on treatment. Commonly cited reasons for treatment discontinuation were drug-related adverse events (AEs) and suboptimal response/treatment failure.
AEs resulted in two deaths with bosutinib (cardiac failure and spindle carcinoma) and in three with imatinib (pneumonia, cerebrovascular accident and sepsis).
The present 24-month data demonstrate bosutinib’s superior efficacy when compared with imatinib, as evidenced by a higher MMR rate and higher cumulative incidence of MMR, CCyR, MR4 and MR4.5, researchers said.
“Safety data were consistent with the known safety profiles of bosutinib and imatinib,” they added. “There were no new safety signals, [and] rates of cardiac and vascular-related AEs remained low.”