Endocrine Adherence in Male Versus Female Breast Cancer: a Seer-medicare Review

Purpose: Breast cancer in men (BC-M) is almost exclusively hormone receptor positive. We conducted a large review of the SEER-Medicare linked database to compare endocrine therapy adherence, discontinuation, and survival outcomes of male versus female patients with breast cancer.

Methods: Study data were obtained through the SEER-Medicare linked database. The study included patients age ≥ 65 years-old diagnosed with breast cancer between 2007 and 2015. The primary endpoints were rates of adherence and discontinuation of endocrine therapy (ET). Adherence was defined as a gap of less than 90 days in-between consecutive Medicare prescriptions. Discontinuation was defined as a gap of greater than 12 months in-between Medicare prescriptions. Secondary endpoint was the association of use of ET with overall survival (OS).

Results: Of the 363 male patients on ET, 214 patients (59.0%) were adherent to the therapy, and 149 patients (41.0%) were nonadherent. Of the 20,722 females on ET, 10,752 (51.9%) were adherent to the therapy, and 9970 (48.1%) were nonadherent. 39 male patients (10.7%) discontinued therapy, while 324 (89.3%) did not discontinue therapy. 1849 female patients (8.9%) discontinued therapy, while 18,873 (91.1%) patients did not. Men were significantly more adherent than women (p = 0.008), but there was no significant difference in discontinuation among men and women (p = 0.228). Survival was significantly improved in both men (HR 0.77, 95% CI 0.60-0.99, p = 0.039) and women (HR 0.84, 95% CI 0.81-0.87, p < 0.001) on ET.

Conclusion: Identification of contributing factors impacting adherence and discontinuation is needed to allow physicians to address barriers to long term use of ET.