A randomized phase II study evaluating different maintenance schedules of nab-paclitaxel in the first-line treatment of metastatic breast cancer: final results of the IBCSG 42-12/BIG 2-12 SNAP trial

Abstract

BackgroundThe phase II SNAP trial was designed to evaluate the efficacy of alternative chemotherapy schedules for prolonged administration in HER2-negative metastatic breast cancer (MBC), after a short induction at conventional doses. Patients and methodsBetween April 2013 and August 2015, 258 women untreated with chemotherapy for MBC were randomly assigned to receive three different maintenance chemotherapy schedules after three cycles of identical induction chemotherapy: arm A, nab-paclitaxel 150mg/m2 days 1 and 15 Q28; arm B, nab-paclitaxel 100mg/m2 days 1, 8 and 15 Q28; arm C, nab-paclitaxel 75mg/m2 days 1, 8, 15 and 22 Q28. Induction was three cycles nab-paclitaxel 150/125mg/m2, days 1, 8 and 15 Q28. The primary objective was to evaluate the efficacy of each maintenance schedule, in terms of progression-free survival (PFS), as compared with the historical reference of 7-month median PFS reported by previous studies with first-line docetaxel. One-sample, one-sided log-rank tests were utilized. Quality-of-life (QoL) evaluation was carried out, and the global indicator for physical well-being was defined as the primary QoL end point; completion rates of QoL forms were >90%. ResultsIn total, 255 patients were assessable for the primary end point. After 18.2-month median follow-up, 182 PFS events were observed. Median PFS was 7.9months [90% confidence interval CI 6.8–8.4] in arm A, 9.0months (90% CI 8.1–10.9) in arm B and 8.5months (90% CI 6.7–9.5) in arm C. PFS in arm B was significantly longer than the historical reference of first-line docetaxel (P=0.03). Grade≥2 sensory neuropathy was reported in 37.9%, 36.1% and 31.2% of the patients in arm A, B and C, respectively (Grade≥3 in 9.1%, 5.6% and 6.6% of the patients, respectively). Noteworthy, the QoL scores for sensory neuropathy did not worsen with prolonged nab-paclitaxel administration in any of the maintenance arms. ConclusionThe SNAP trial demonstrated that alternative nab-paclitaxel maintenance schedules with reduced dosages after a short induction at conventional doses are feasible and active in the first-line treatment of MBC.Registration: ClinicalTrials.gov NCT01746225