Clinical Benefit Rate and Time to Response in RIBBON-1, a Randomized, Double-Blind, Phase III Trial of Chemotherapy with or without Bevacizumab (B) for the First-Line Treatment of HER2-Negative Locally Recurrent or Metastatic Breast Cancer (MBC).

Abstract

Abstract BackgroundRIBBON-1, a Phase III, multicenter, randomized, placebo-controlled trial in patients with previously untreated MBC was designed to evaluate the efficacy and safety of adding bevacizumab (B) to chemotherapy regimens including capecitabine (Cape; n=615); a taxane (T; n=307), or an anthracycline (Anth; n=315) compared with chemotherapy alone. Pre-specified analyses of progression-free survival PFS) in the Cape and pooled T/Anth cohorts, the primary endpoints of the study were increased upon addition of B. In the Cape cohort, median PFS increased from 5.7 to 8.6 mo (HR=0.69, p-value=0.0002) and in the T/Anth cohort, it increased from 8.0 to 9.2 mo (HR=0.64; p-value<0.0001).MethodsRECIST was used to determine objective response rate (ORR). Patients without a post-baseline tumor assessment were considered non-responders. The primary analysis for the ORR and the duration of response was performed using only patients with measurable disease at baseline. ORR was formally compared between the two treatment arms using the Mantel-Haenszel Chi-squared test, using the randomization stratification factors. Fisher's exact test was also performed. Clinical benefit rate (CBR) was defined as the proportion of patients with a complete or partial response or with stable disease at Week 24. Exploratory analyses of CBR and time to response are provided here. Summary statistics of time to response at Week 9 will be presented as will the final analysis of the secondary endpoint of overall survival.ResultsAnalyses of ORR and CBR are provided in the following table. CapeTaxaneAnth PL (n=206)B (n=409)PL (n=104)B (n=203)PL (n=103)B (n=212)Patients with measurable disease, n (%)161 (78.2)325 (61.1)85 (81.7)161 (79.3)92 (89.3)184 (86.8)ORR, %23.635.435.350.340.252.2CR, n (%)1 (0.6)7 (2.2)3 (3.5)4 (2.5)2 (2.2)3 (1.6)PR, n (%)37 (23.0)108 (33.2)27 (31.8)77 (47.8)35 (38.0)93 (50.5)Difference between arms, %11.815.012.0p-value, unstratified0.00940.030.073Duration of ORMedian, mo7.29.28.68.46.08.1HR (95% CI)0.61 (0.39–0.96)0.75 (0.45–1.27)0.53 (0.34–0.83)Log-rank p-value0.03260.2840.0047Clinical benefit rate*, %47.164.365.471.969.980.7p-value, unstratified<0.00010.240.04CR+PR at Week 9, %20.229.438.354.544.451.1B=bevacizumab, cape=capecitabine, CI=confidence interval, HR=hazard ratio, OR=objective response, PL=placebo, T/Anth=taxane/anthracycline.*For randomized patients.ConclusionsIn patients with HER2-negative MBC, the addition of bevacizumab to capecitabine, taxane or anthracycline chemotherapy induces more responses and those responses occur more rapidly. For capecitabine and anthracycline the addition of bevacizumab leads to objective responses that last longer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6084.