First-line patterns of care and outcomes of HER2-positive breast cancer patients who progressed after receiving adjuvant trastuzumab in the outpatient community setting.

Abstract

684 Background: Trastuzumab (T) is indicated in the adjuvant and first-line setting for HER2+ breast cancer patients (pts). The purpose of this retrospective study was to evaluate community-based patterns of care and outcomes following disease progression (DP) among pts who received T in the adjuvant setting. Methods: Using US Oncology's iKnowMed EMR data, we identified adjuvant HER2+ pts who received T from 1/1/2006–7/31/2007. Pts were followed through 8/31/2009 to observe DP and post-progression patterns of care and outcomes. Pts who experienced DP were assigned to cohorts based on whether they received T in the first-line setting. Overall (OS) and progression-free survival (PFS) were compared by cohort using Kaplan-Meier and Cox regression analysis. To account for survivorship bias, landmark analyses were conducted at 120 and 180 days to examine residual PFS and OS, defined as time from landmark to DP or death. Results: Of 2,049 pts who received adjuvant T, 164 (8%) experienced DP and received first-line care during the study period. Of these 164 pts, 122 (74%) continued to receive T ± chemo for first-line therapy while 42 (26%) received chemotherapy only. Observed OS and PFS was significantly longer for pts who received first-line T compared to those who did not (Mean PFS > 590 vs. 362 days, log-rank p < 0.001; Mean OS > 733 vs. 535 days, log-rank p > 0.04). In Cox regression analyses using backwards elimination, first-line T remained significantly associated with PFS (HR: 0.39; 95% CI > 0.19 – 0.80), but not OS (0.61; 95% CI > 0.27 – 1.35) after considering age, performance status, ER/PR status, stage at diagnosis, adjuvant T duration, and time to progression from adjuvant to metastatic disease as covariates. In landmark analyses among pts who were progression-free at 120 days, longer T duration was associated with increased residual PFS (p-trend > 0.02) and OS (p-trend > 0.04). Among patients who were progression-free at 180 days, longer T duration was associated with increased residual PFS (p-trend > 0.04), but not OS. Conclusions: Results of this study among pts who received adjuvant T suggest that continuing T following DP may provide clinical benefit in the outpatient community setting. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Genentech Genentech Genentech Genentech Genentech