Adjuvant Radiotherapy After Radical Cystectomy for Patients with High-risk Muscle-invasive Bladder Cancer: Results of a Multicentric Phase II Trial

Background: High-risk muscle-invasive bladder cancer (MIBC) has a poor prognosis. Old trials showed that external beam radiotherapy (EBRT) after radical cystectomy (RC) decreases the incidence of local recurrences but induces severe toxicity.

Objective: To evaluate the toxicity and local control rate after adjuvant EBRT after RC delivered with volumetric arc radiotherapy.

Design, Setting, And Participants: This is a multicentric phase 2 trial. From August 2014 till October 2020, we treated 72 high-risk MIBC patients with adjuvant EBRT after RC. High-risk MIBC is defined as ≥pT3-MIBC ± lymphovascular invasion, fewer than ten lymph nodes removed, pathological positive lymph nodes, or positive surgical margins.

Intervention: Patients received 50 Gy in 25 fractions with intensity-modulated radiotherapy to the pelvic lymph nodes ± cystectomy bed.

Outcome Measurements And Statistical Analysis: The primary outcome is acute toxicity. We report on local relapse-free rate (LRFR), clinical relapse-free survival (CRFS), overall survival (OS), and bladder cancer-specific survival (BCSS).

Results And Limitations: The median follow-up is 18 mo. Forty-two patients (61%) developed acute grade 2 gastrointestinal (GI) toxicity. Four patients (6%) had acute grade 3 GI toxicity. One patient had grade 5 diarrhea and vomiting due to obstruction at 1 mo. Two-year probabilities of developing grade ≥3 and ≥2 GI toxicity were 17% and 76%, respectively. Urinary toxicity, assessed in 17 patients with a neobladder, was acceptable with acute grade 2 and 3 urinary toxicity reported in 53% (N = 9) and 18% (N = 3) of the patients, respectively. The 2-yr LRFR is 83% ± 5% and the 2-yr CRFS rate is 43% with a median CRFS time of 12 mo (95% confidence interval: 3-21 mo). Two-year OS and BCSS are 52% ± 7% and 62% ± 7%, respectively. Shortcomings are the nonrandomized study design and limited follow-up.

Conclusions: Adjuvant EBRT after RC can be administered without excessive severe toxicity.

Patient Summary: In this report, we looked at the incidence of toxicity and local control after adjuvant external beam radiotherapy (EBRT) following radical cystectomy (RC) in high-risk muscle-invasive bladder cancer patients. We found that adjuvant EBRT was feasible and resulted in good local control. We conclude that these data support further enrollment of patients in ongoing trials to evaluate the place of adjuvant EBRT after RC.