266P - Is the overall survival after hormone therapy for hormone-receptor-positive, HER2-negative metastatic breast cancer still better than for triple-negative metastatic breast cancer?

Abstract

Hormone-receptor-positive (HR+) HER2-negative (HER2-) metastatic breast cancer (MBC), i.e. luminal-type MBC, is known to have a better prognosis than triple-negative MBC (TNMBC). However, if HR + HER2-MBC patients (pts) are diagnosed to be resistant to hormone therapy (HTx), they must undergo chemotherapy (CTx), just like TNMBC pts. To our knowledge, however, the overall survival (OS) after HTx (the OS derived from CTx) has not been well discussed. We herein reviewed our medical records from 2002 to the present to assess the OS beyond HTx and identify the prognostic factors in HR + HER2-MBC pts. Statistical analyses were performed using the Kaplan-Meyer method and a multivariate COX regression analysis. We identified 344 HR + HER2-MBC pts from our medical records, and 286 (207 recurrent [rBC], 79 advanced [aBC]) underwent CTx. Among those 286 pts, 239 (83.6%) received at least 1 or more HTx sessions prior to CTx, while the other 47 (16.4%) received CTx as their initial systemic therapy. We also extracted 95 (69 rBC, 26 aBC) TNMBC pts from the records as a control group. The median OS for the 286 pts from the diagnosis of MBC was 1395.0 days (95% confidence interval [CI] 500.0-3942.0), which was superior to that of TNMBC pts (777.0 days, 95%CI 238.0-1784.0, p < 0.001, log-rank). The median OS from the initiation of CTx was 972.0 days (95%CI 294.0-2285.0) in HR + HER2-MBC pts, which was significantly (p < 0.01, log-rank) better than that in TNMBC pts. However, when limited to rBC pts, who comprise the majority of ER + HER2-MBC pts, the OS from the initiation of CTx was almost the same as that of TNrBC pts (median 932.0 and 866.0, respectively, p = NS). Multivariate analyses further revealed that rBC pts who had a disease-free interval (DFI) of less than 24 months or pts who had bone lesions at the initiation of CTx showed a significantly poorer prognosis than those who had a longer DFI or no bone lesions (hazard ratio of 1.50 [95%CI 1.01-2.23] and 1.57 [1.02-2.40], respectively). Our single-institution retrospective analysis with some limitations found that the OS after HTx in recurrent HR + HER2-BC pts was almost identical to that of recurrent TNBC pts.