Use and Effectiveness of Adjuvant Endocrine Therapy for Hormone Receptor-Positive Breast Cancer in Men.

Importance: Although adjuvant endocrine therapy confers a survival benefit among females with hormone receptor (HR)-positive breast cancer, the effectiveness of this treatment among males with HR-positive breast cancer has not been rigorously investigated. Objective: To investigate trends, patterns of use, and effectiveness of adjuvant endocrine therapy among men with HR-positive breast cancer. Design, Setting, and Participants: This retrospective cohort study identified patients in the National Cancer Database with breast cancer who had received treatment from 2004 through 2014. Inclusion criteria for the primary study cohort were males at least 18 years old with nonmetastatic HR-positive invasive breast cancer who underwent surgery with or without adjuvant endocrine therapy. A cohort of female patients was also identified using the same inclusion criteria for comparative analyses by sex. Data analysis was conducted from October 1, 2017, to December 15, 2017. Exposures: Receipt of adjuvant endocrine therapy. Main Outcomes and Measures: Patterns of adjuvant endocrine therapy use were assessed using multivariable logistic regression analyses. Association between adjuvant endocrine therapy use and overall survival was assessed using propensity score-weighted multivariable Cox regression models.
Results: The primary study cohort comprised 10 173 men with HR-positive breast cancer (mean [interquartile range] age, 66 [57-75] years). The comparative cohort comprised 961 676 women with HR-positive breast cancer (mean [interquartile range] age, 62 [52-72] years). The median follow-up for the male cohort was 49.6 months (range, 0.1-142.5 months). Men presented more frequently than women with HR-positive disease (94.0% vs 84.3%, P < .001). However, eligible men were less likely than women to receive adjuvant endocrine therapy (67.3% vs 79.0%; OR, 0.61; 95% CI, 0.58-0.63; P < .001). Treatment at academic facilities (odds ratio, 1.13; 95% CI, 1.02-1.25; P = .02) and receipt of adjuvant radiotherapy (odds ratio, 2.83; 95% CI, 2.55-3.15; P < .001) or chemotherapy (odds ratio, 1.20; 95% CI, 1.07-1.34; P < .001) were statistically significantly associated with adjuvant endocrine therapy use in men. A propensity score-weighted analysis indicated that relative to no use, adjuvant endocrine therapy use in men was associated with improved overall survival (hazard ratio, 0.70; 95% CI, 0.63-0.77; P < .001). Conclusions and Relevance: There is a sex disparate underuse of adjuvant endocrine therapy among men with HR-positive breast cancer despite the use of this treatment being associated with improved overall survival. Further research and interventions may be warranted to bridge gaps in care in this population.