Maximizing survival in patients with muscle-invasive bladder cancer undergoing curative bladder-preserving radiotherapy: the impact of radiotherapy dose escalation

Abstract

Most historic trials demonstrating the outcomes with bladder-preserving radiotherapy (RT) used 64–66 Gy. However, newer data suggest improved outcomes with dose escalation up to 70 Gy. Our objective was to explore the impact of dose escalation on overall survival (OS) and to identify the optimal radiotherapy (RT) dose in patients with muscle-invasive bladder cancer (MIBC) treated with curative bladder-preserving RT. We conducted a retrospective cohort study of patients with cT2–4 N0–3 M0 transitional cell MIBC who were treated with curative RT (60–70 Gy in 1.8–2.0 Gy/fraction) using the National Cancer Database. Univariable (UVA) and multivariable (MVA) frailty survival analyses were employed to identify the association of dose escalation to 67–70 Gy, as well as different RT dose subgroups within 60–66 Gy, and OS. In total, 2531 patients met eligibility criteria. The 2-year OS was 53 and 56%, respectively, for patients receiving 60–66 and 67–70 Gy (p = .25). On MVA, there was no significant difference in survival for patients receiving 67–70 vs. 60–66 Gy (hazard ratio [HR], 0.91; 95% confidence interval [CI], 0.76–1.10; p = .33). Compared to doses of 64–66 Gy, OS was worse with 60–61 Gy (HR, 1.33; 95% CI, 1.17–1.52; p < .0001) but there was no difference in OS with 62–63 Gy (HR, 1.11; 95% CI, 0.96–1.28; p = .15) after adjusting for clinical T stage and Charlson-Deyo comorbidity score. When treating patients with MIBC with curative bladder-preserving radiotherapy, RT doses of 62–66 Gy have improved OS compared to lower doses, while dose escalation to 67–70 Gy does not improve survival. Our study does not support deviating from the standard of 64–66 Gy.