AbstractBackground Breast cancers expressing low (1-9%) immunohistochemistry levels of estrogen and progesterone hormone receptors (HR), remain an uncertain category, being considered either as triple negative (TN) breast cancers or HR-positive (HR+) tumors across guidelines or approvals. Methods ESME is a National real-world cohort of all consecutive patients who initiated a first-line treatment for metastatic breast cancer (MBC) from year 2008 onwards in one of the 18 French Comprehensive Cancer Centers. We analyzed baseline data and outcomes from all patients with HER2-negative MBC and known HR expression levels. Our primary objective was to evaluate overall survival (OS) in HR-low MBC patients compared with those with TN and HR+ disease. Results Out of 30,459 patients in the ESME database who initiated an MBC treatment between 01/2008 and 01/2021, 19,109 were eligible for this analysis: 16768, 2113, 228 respectively with HR+, TN, and HR-low MBC. Median follow-up was 58.0 months (56.6-59.0). Median OS were 44.6 (43.8-45.5), 19.1 (15.5-22.4) and 15.7 (15.0-16.8) months in the HR+, TN, and HR-low groups, respectively. The multivariable analysis identified no difference in OS between HR-low and TN groups (Hazard Ratio 0.93, 95%CI 0.77-1.11). Median PFS under first line chemotherapy were 10.2 (9.9-10.6), 5.3 (5.1-5.6) and 5.1 (4.1-6.2) months for HR+, TN and HR-low groups, respectively. In the multivariable analysis, the HR-low group had a statistically poorer PFS compared to the TN group (Hazard Ratio 1.24, 95% CI 1.04-1.49). Conclusions In this large cohort, patients with HR-low MBC have the same dismal overall survival as those with TN MBC.
Alexandre et al. (Fri,) studied this question.