Abstract P2-10-21: Prognostic value of estrogen receptor status in women with synchronous or metachronous breast cancers

Abstract

Abstract Background: Estrogen receptor (ER) is an important prognostic and predictive factor for breast cancer (BC) patients. For women with two primary breast cancers, however, estrogen receptor status measured at the two tumors is not always the same, either due to tumor heterogeneity, or because of limited reproducibility of receptor assays. For women with metachronous breast cancers, it is unclear if estrogen receptor status of previous cancer has prognostic value. For women with synchronous breast cancers, it is important to know if inconsistent receptor status predicts worse clinical outcome. Methods: Data on ER status of two primary breast cancers were obtained from the Surveillance, Epidemiology, and End Results program 1990–2009. We used piecewise proportional hazard Cox models to examine the joint effect of ER statuses of two tumors on overall survival or disease-free survival. Hazard ratio (HR) and 95% confidence interval (CI) were calculated, after adjusting for age, stage, race/ethnicity, histology, grade, and treatments in Cox models. Synchronous and metachronous cases were analyzed separately. Results: There are 12,285 patients with synchronous breast cancers; 81.2% had both tumors being ER positive, 10.2% had one tumor being ER positive but the other being ER negative, and 5.6% had both tumors being ER negative. As shown in the Table, patients with inconsistent ER status (heterogeneity) had worse short-term survival rate than patients with double ER positive tumors. Among the 14,470 patients with metachronous breast cancers, 60.2% had two ER+ tumors, 13.8% had two ER− tumors, 11.8% had ER status changing from negative to positive, and 14.1% had ER status changing from positive to negative. In addition to ER status of the index cancer, ER status of the first cancer has independent prognostic value in predicting both short-term and long-term outcome (p = 0.0002). Conclusions: Our study found that estrogen status of previous cancer has independent prognostic value for women with metachronous breast cancers. We also found that inconsistency in ER status between two tumors predicts worse survival for women with synchronous breast cancer. These findings suggest that heterogeneity or change in estrogen receptor expression in patients with two breast cancers should be considered during decision making on treatment or counseling on prognosis. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-21.