Clinical, therapeutic and prognostic differences between male and female patients with breast cancer-a comparison of 2510 men and 307,634 women in a registry-based study in Germany.

Purpose: The aim of the present study was to compare patient, tumor characteristics and prognostic factors as well as diagnostics and therapies between men and women with breast cancer. The rates of primary distant metastases, contralateral second tumors, overall survival (OS), recurrence, and recurrence-free survival (RFS) were analyzed and compared between men and women.

Methods: This retrospective cohort study included patient data from 18 clinical cancer registries in Germany (2000-2018). Differences in risk factors and short-term endpoints were analyzed via univariable and multivariable binary logistic regression analyses. OS, RFS, and the rate of subsequent second tumors were examined via Kaplan‒Meier, univariable and multivariable Cox regression methods.

Results: Compared with women, male patients with breast cancer presented a significantly greater risk of unfavorable prognostic factors, such as advanced stage, lymphatic invasion, and more primary distant metastases. While sentinel lymph node biopsy and HER-2 testing were comparable, treatment rates for men were 9.5-29.0% lower than those for women. In multivariable analyses, men had a 1.32-fold increased risk of death (95% CI 1.24-1.41; p < 0.001). The risk of recurrence/mortality was significantly increased by a factor of 1.531 (95% CI 1.43-1.65; p < 0.001). Adjustment for therapy in a multivariable regression model did not significantly affect the risk of death. Nevertheless, men had a survival benefit from systemic therapies comparable to that of women.

Conclusion: Neither patient and tumor characteristics nor differences in therapy could completely explain the difference in mortality between men and women. Differences in lifestyle or biological factors could play a role.