Use and duration of chemotherapy (CT) in patients (pts) with metastatic breast cancer (MBC) according to tumor subtype (TS) and line of therapy (tx).

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6089 Background: Benefits of CT vary widely in MBC pts. We aimed to describe the impact of breast cancer TS and line of tx on the duration of CT. Methods: In a retrospective analysis, we identified 205 pts treated with CT for MBC at the Dana-Farber Cancer Institute between 2005-8. TS were classified as hormone receptor (HR)+ (ER+/PR+/HER2-), triple negative (TN) (ER-/PR-/HER2-) or HER2+ (HER2+, any HR). CT duration was defined as "time from start of one CT line to the start of the next CT." Chi-square, Kruskal-Wallis, and Kaplan-Meier methods were used. Results: Median follow-up was 54 months (m). Most pts had received adjuvant tx, though 23% had MBC at diagnosis. Almost all HER2+ pts had concurrent anti-HER2 tx. CT duration was longest in 1st line with consecutive stepwise decrease. The proportion of pts who received CT beyond the 3rd line varied by TS: 52% of HER2+ pts received > 4 CT lines, compared with 37% of HR+ and 29% of TN pts. Duration in later CT lines also differed by TS. Median CT duration in HER2+ pts was > 4 m in all 6 lines, but HR+ and TN pts had a median CT duration of <4m from the 4th line onwards. Quartile estimates suggested a substantial fraction of HER2+ and HR+ pts receiving >6m of CT in 5th and 6th line; by contrast, CT duration for TN pts were consistently brief in later CT lines. Conclusions: TS determines the likely duration and number of lines of CT for MBC. Among HR+ and HER2+ pts who receive CT beyond 3rd line, there are substantial rates of prolonged tx suggesting clinical benefit. For TN pts, the opportunity for additional lines and the CT duration declined more dramatically. The true role of advanced (> 3rd) CT lines for all MBC in improving quality of life, survival, and the predictors of such benefit, warrant further study. [Table: see text]

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