Abstract
Abstract Background We previously reported the results of a phase II study evaluating the efficacy and safety of 3 different dosing regimens of ab-pac and docetaxel for the first-line treatment of MBC (Gradishar et al. J ClinOncol. 2009;27:3611). Here we report outcomes for a subset of patients (pts) during treatment with ab-pac at 150 mg/m2 weekly for the first 3 weeks of a 4-week schedule (qw 3/4). Methods: Patients (N = 300) with previously untreated MBC were randomized to 1 of 4 treatment arms: arm A, ab-pac at 300 mg/m2 q3w; arm B, ab-pac at 100 mg/m2 qw 3/4; arm C, ab-pac at 150 mg/m2 qw 3/4; arm D, docetaxel at 100 mg/m2 q3w. A step-down statistical approach was used for pairwise comparisons of treatment groups. The trial was powered for antitumor activity and safety. Results: Treatment arm C produced the longest overall survival (OS) (33.8 months) with an 11.6-month longer median OS vs arm B (22.2 months, HR 0.575; P = .008) and a 7.2-month longer median OS vs arm D (26.6 months, HR 0.688; P not statistically significant). Median OS in arm A was 27.7 months. These OS data were consistent with previously published overall response rates (ORR) and progression-free survival (PFS). Forty-seven percent of pts in arm C required dose reduction due to toxicity, including 27% due to neutropenia (np), 15% due to sensory neuropathy (SN), 3% due to allergy/immunology, 1% due to febrile np, and 1% due to ulceration of the skin. The median OS for the subset of pts requiring DRs in arm C was comparable to pts not dose reduced: 35.2 and 31.8, respectively. Pts who were dose reduced in arm C received a median of 2 additional cycles of treatment compared with those without DRs: 10 (range 2 — 27) vs 8 (range 1 — 27). Investigator assessed ORR and PFS were numerically higher in pts dose reduced vs those not reduced. Baseline characteristics were similar between pts requiring DRs vs not. qw 3/4, first 3 out of 4 weeks; CI, confidence interval; ECOG PS, Eastern Cooperative Oncology Group performance status. aInvestigator assessed. bAll grade 3, no grade 4. Conclusion: Pts in the ab-pac 150 mg/m2qw 3/4 arm who were dose reduced achieved a similar OS compared to patients who were not dose reduced. No clear trends in baseline characteristics emerged to predict the requirement for dose reduction in the 150 mg/m2 ab-pac arm. The ab-pac 150 mg/m2 qw 3/4 dosing regimen provided a survival advantage in this phase II trial in first-line MBC and dose reductions could be used to manage toxicities and prolong treatment duration without compromising efficacy. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-19-13.
Published Version
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