Androgen receptor expression and breast cancer mortality in a population-based prospective cohort

Purpose

The increase in clinical trials with androgen receptor (AR)-targeting drugs emphasizes the need of clarifying the role of AR expression in different breast cancer subtypes. AR confers good prognosis in estrogen receptor positive (ER+) breast cancer, but its role in ER-negative (ER?) breast cancer is unclear. The aim of this study was to elaborate on previous findings of a differential prognostic role for AR depending on ER status, using breast cancer mortality (BCM) as endpoint, in a population-based cohort from the Malmö Diet and Cancer Study.

Methods

Immunohistochemical AR expression was assessed in 910 women with invasive breast cancer diagnosed 1991–2010, supplemented with clinicopathological information, vital status, and cause of death, with the last follow-up in December 2014 (median 10 years). Survival analyses according to AR status and AR/ER combinations were performed.

Results

AR expression was available for 671 tumors. AR+ (n = 573, 85%) was associated with favorable established tumor markers and lower BCM in univariable analysis, especially during the first 5 years following diagnosis [HR 0.4; 95% confidence intervals (CI) 0.2–0.7]. Multivariable analysis for short-term follow-up indicated higher BCM among patients with AR+ER? tumors (HR 3.5; 95% CI 1.4–9.1) than other AR and ER combinations.

Conclusions

AR expression added prognostic information to ER expression with respect to short-term prognosis. The worst prognosis was seen for patients with AR+/ER? tumors in short-term follow-up, supporting the pre-specified hypothesis. However, larger cohorts are needed for further characterization of the role of AR expression in ER? breast cancer.