Benefit of chemotherapy after third line and evaluation of post-progression survival (PPS) in metastatic breast cancer (MBC): A single institution study.

Abstract

e11517 Background: MBC remains an incurable disease with median survival of 2-3 years despite new drugs. The gain of benefit from third-line chemotherapy (CT3) in MBC is unknown. The validation of PPS as surrogate endpoint and its correlation to OS is under debate. Methods: From 2006-2012 we analyzed retrospectively consecutive 114 pts treated for MBC, 67 with at least 3 lines CT, to show the gain of benefit after CT3 and predictive factors of response to multiple lines of therapy. Moreover, we evaluated PPS for each line and its relation to OS. Results: Median age at M+ diagnosis was 58 years (29-87), median site of disease 2 (1-6), 66.7% visceral, HER-2+ pts 31.1%, median number of anti-Her-2 treatment 2 (1-6); 56.1% received a maintenance treatment (37% M1, 13% M2), median number of treatment 3 (1-8). Median OS for all pts was 47.1 (95%CI: 36.5-57.6). No difference in OS for pts with maintenance treatment vs not, respectively 49.1 vs 45.6 P=0.17. Multivariate Cox analysis showed that OS is related with ER/Pgr status (positive vs negative p=0.03) number of lines ( >3 vs ≤ 3) p< 0.0001 and number of metastatic sites (>2 vs ≤2) p=0.01. We evaluated relation between PFS and OS and PPS and OS until 6th line of therapy with a linear regression model. Conclusions: These results supported the use of chemotherapy after CT3. PFS and PPS are related to OS until 6th line of treatment. PPS as surrogate endpoint of OS is a valid hypothesis to be evaluated in prospective trials of MBC [Table: see text]