A prospective cohort study of clinical characteristics and outcomes in Chinese patients with estrogen receptor-negative/progesterone receptor-positive early breast cancer

PURPOSE: This study aimed to examine the clinical characteristics and outcomes of patients with estrogen receptor-negative (ER−)/progesterone receptor-positive (PR+) early breast cancer. We also aimed to investigate the benefits of adjuvant endocrine therapy (ET) in this patient population. METHODS: Patients with early breast cancer diagnosed at West China Hospital were divided into the ER−/PR+, ER+, and ER−/PR− groups. The chi-square test was used to analyze differences in clinical and pathological features among the groups. Multivariable Cox and Fine–Gray regression models were used to compare mortality and locoregional recurrence (LRR)/distant recurrence (DR), respectively. We performed a subgroup analysis to determine which ER−/PR+ patients can benefit more from ET. RESULTS: From 2008 to 2020, we enrolled 443, 7104, and 2892 patients into the ER−/PR+, ER+, and ER−/PR− groups, respectively. The ER−/PR+ group showed more unfavorable clinical features and aggressive pathological characteristics than the ER+ group. The mortality, LRR, and DR rates were higher in the ER−/PR+ than in the ER+ group. Most clinical features and pathological characteristics were similar between the ER−/PR+ and ER−/PR− group and their outcomes were comparable. In the ER−/PR+ group, patients who received ET showed significantly lower LRR and mortality rates than those who did not; however, no difference was observed in DR. Subgroup analysis suggested that ER−/PR+ patients age ≥ 55 years, and postmenopausal status can benefit from ET. CONCLUSION: ER−/PR+ tumors have more aggressive pathological characteristics and more unfavorable clinical features than ER+ tumors. ET can reduce the LRR and mortality rates in ER−/PR+ patients. Postmenopausal and age ≥ 55 years ER−/PR+ patients can benefit from ET. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10549-023-06964-6.