Combination versus sequential chemotherapy for metastatic breast cancer: An evaluation of outcomes from a community oncology network.

Abstract

6106 Background: There is wide variability in the treatment of metastatic breast cancer (MBC). Debate exists regarding the relative benefits of combination vs. sequential chemotherapy. Combination therapy may improve response rates, but its effect on overall survival (OS) is not clear. This study evaluated OS for MBC patients receiving combination vs. sequential therapy starting with second-line therapy. Methods: Using the iKnowMed electronic medical record database from the US Oncology network, patients with MBC who initiated second-line chemotherapy between July 2006 and July 2009 were included in this retrospective analysis. Combination therapy was allowed in all patients for first-line therapy only. Group A patients were treated with sequential single-agent chemotherapy (other than first-line). Group B patients received combination chemotherapy at any time beyond first-line. The primary endpoint was OS (from time of initiation of second-line chemotherapy to death). A documented date of death was required for inclusion. Patients with HER2-positive disease were excluded. Patients were characterized with respect to age, Karnofsky performance status, hormone receptor status, visceral vs. bone-only metastases, and lines of therapy. OS was compared using the Kaplan Meier method. Results: 263 patients were included. 135 patients received single-agent therapy (Group A) and 128 patients received combination therapy (Group B). There was a 1.1 month difference in median OS, which was not significant (6.5 months in Group A vs. 7.6 months in Group B; p = 0.1493; hazard ratio = 0.8356; 95% CI = 0.6550 to 1.0665). The groups were well balanced with respect to age, hormone receptor status, and types of metastases. Patients receiving combination therapy tended to have slightly higher performance status. Median number of lines of therapy for MBC was 3 (Group A) vs. 4 (Group B). Conclusions: These findings, incorporating real-world variability in the treatment of MBC, support the concept that combination chemotherapy beyond first-line does not significantly prolong survival compared to sequential monotherapy. Because MBC is incurable, OS, toxicities, and costs are important treatment considerations. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration US Oncology