Effect of Sex Differences on Cancer Outcomes After Chemo-Radiation for Muscle-Invasive Bladder Cancer: A Retrospective Multicenter Cohort Study

Abstract

Objective: To examine whether the well demonstrated sex-based differences in bladder cancer management and outcomes are similarly observed for those treated with chemo-radiation for muscle invasive bladder cancer (MIBC).

Methods: This retrospective, multicenter study reports on patients who underwent curative intent radiotherapy, with concurrent chemotherapy, for MIBC across 10 academic centers in Canada. The primary outcome was cancer specific survival (CSS) and secondary outcomes included complete response and overall survival (OS). Survival was estimated using the Kaplan-Meier method. Multivariable regression models were performed to assess an independent association of sex on outcomes.

Results: There were 397 males and 145 females who underwent curative intent chemo-radiation for MIBC with a total median follow-up of 30 months. Baseline cancer characteristics and treatment specifics were similar between the sexes, although complete resection was more common in males and hydronephrosis was more common in females. There were no differences in complete response rates between males and females (72.3% vs 73.1%). The 3-year CSS was 78.4% vs 70.4% for males and females respectively and median OS was 81 months vs 52 months. Cumulative incidence of mortality was similar between the sexes with organ-confined disease but higher for females with non-organ-confined disease. In multivariable analysis, sex was independently associated with CSS (HR 1.46, 95% CI 0.95-2.24) but not OS.

Conclusion: This multicenter study demonstrated worse CSS in females undergoing chemo-radiation. Future investigations should explore potential effects from differences in staging, as well as other biological- and treatment-related factors, including differential responses to chemo-sensitized radiation.