ER+/PR- (estrogen receptor positive and progesterone receptor negative) tumors constitute only a small portion of the breast cancer population. Patients with ER+/PR- tumors, however, are characterized by worse survival compared to patients with ER+/PR+ (estrogen receptor positive and progesterone receptor positive) tumors. Controversy exists regarding the efficacy of hormone blocking therapy for patients with ER+/PR- tumors. The NCDB was queried between 2004 and 2015, and patients with invasive ER+/PR- tumors were identified. We employed univariate Cox proportional hazards to compare outcomes among patients that did or did not receive hormone blocking therapy. We identified 138,398 patients with invasive ER+/PR- tumors, 32,044 (23%) of whom did not receive hormone blocking therapy. The reasons for not receiving hormone blocking therapy included contraindications to treatment, death, patient refusal, and unknown. There were no significant differences in race, income quartile, or education quartile between patients who did and did not receive hormone blocking therapy. Patients who did not receive hormone blocking therapy underwent surgical assessment of the axilla more frequently than those who did receive hormone therapy. Our analysis demonstrated that hormone blocking therapy administration was associated with increased overall survival for up to 10 years of follow up (HR: 0.58; 95% CI: 0.56-0.59, p < 0.001). Hormone blocking therapy may be associated with increased survival for breast cancer patients with ER+/PR- tumors. Although this benefit may last for years after completion of the course, up to 25% of patients do not receive this treatment. Strategies to increase the utilization and adherence to hormone blocking therapy regimens may improve patient survival outcomes.
Keywords: Breast cancer; ER+/−; Hormone therapy; PR+/−.