Association of estrogen receptor status with survival outcomes in neuroendocrine carcinoma of the breast: A SEER Research Plus analysis (2010–2021).

Abstract

e12759 Background: Neuroendocrine carcinoma of the breast (NECB) is a rare histologic sub-type with heterogeneous clinical behavior. Although NECB is frequently hormone receptor–positive, the prognostic relevance of estrogen receptor (ER) status remains incompletely defined due to evolving histologic classifications and reliance on small, heterogeneous series. We evaluated survival outcomes by ER status using a contemporary population-based cohort. Methods: We identified malignant NECB cases diagnosed between 2010 and 2021 in the SEER Research Plus database and restricted analyses to first primary tumors with known ER status. ER status was defined using SEER breast ER re-code variables (ER-positive coded as 0; ER-negative coded as 1). Observed overall survival (OS) was summarized at 1–5 years, and median observed survival was estimated using SEER*Stat survival analyses. Survival patterns were further examined in analyses stratified by stage at diagnosis, age, and receipt of surgery. Results: Among 221 patients with NECB and known ER status, 159 (72.0%) were ER-positive and 62 (28.0%) were ER-negative. Median observed survival was not reached in the ER-positive group compared with 55.8 months in ER-negative disease. ER-positive NECB demonstrated superior observed survival across all evaluated time-points, including 1-year OS (87.5% vs 75.6%), 3-year OS (76.2% vs 55.8%), and 5-year OS (65.4% vs 47.4%) for ER-positive versus ER-negative tumors, respectively. The survival advantage associated with ER-positive NECB persisted in analyses stratified by stage at diagnosis, age, and receipt of surgery. Conclusions: In this contemporary population-based analysis, ER-positive NECB was associated with substantially improved survival compared with ER-negative disease. These findings support ER status as a clinically relevant prognostic factor in NECB and provide contemporary survival benchmarks that may inform risk stratification and future outcomes research in this rare breast cancer sub-type.