Abstract PS5-45: The impact of progesterone receptor negativity on oncologic outcomes in estrogen receptor positive breast cancer

Abstract

Abstract BACKGROUND: Estrogen receptor (ER) status provides invaluable prognostic and therapeutic information in breast cancer (BC). When clinical decision making is driven by ER status, the value of assessing progesterone receptor (PgR) status is less certain. AIM: To describe the clinicopathologic features of ER positive (ER+) /PgR negative (PgR-) BC and to determine the effect of PgR negativity on oncologic outcomes in ER+ disease.METHODS: Consecutive female patients with ER+ BC managed in a single institution between 2005-2015 were included. Clinicopathological features of PgR- BC were determined. Factors associated with PgR- disease were assessed using binary logistic regression. Oncological outcome was assessed using Kaplan-Meier curves and Cox regression analysis.RESULTS: 2660 patients were included with a median age of 59.6±13.3 years (21-99). Median follow-up was 97.2 months (3.0-181.2). 2208 cases were PgR+ (83.0%) and 452 were PgR- (17.0%). Being postmenopausal (OR:1.656, 95% Confidence interval (CI):1.249-2.195, P<0.001), presenting with symptoms (OR:1.712, 95% CI:1.302-2.249, P<0.001), invasive ductal subtype (OR:1.514, 95% CI:1.166-1.966, P=0.002) and grade 3 tumours (OR:2.198, 95% CI:1.683-2.870, P<0.001) were all associated with PgR- status. In patients receiving neoadjuvant chemotherapy (n=308), pathological complete response rates were 10.1% (25/247) in patients with PgR+ disease, versus 18.0% in those with PgR- disease (11/61) (P=0.050). PgR negativity independently predicted worse disease-free (HR:1.632, 95%CI:1.209-2.204, P=0.001) and overall survival (OS) (HR:1.774, 95%CI:1.324-2.375, P<0.001), as well as worse OS in ER+/HER2- disease (P=0.004). CONCLUSIONS: In ER+ disease, PgR- tumours have more aggressive clinicopathological features and worse oncological outcomes. Neoadjuvant and adjuvant therapeutic strategies should be tailored according to PgR status. Citation Format: Matthew G Davey, Éanna J Ryan, Padraig J Folan, Niamh O'Halloran, Michael R Boland, Michael Kevin Barry, Karl J Sweeney, Carmel M Malone, Ray J McLaughlin, Michael J Kerin, Aoife J Lowery. The impact of progesterone receptor negativity on oncologic outcomes in estrogen receptor positive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-45.