KEY POINTS
- This multicentre retrospective analysis included 107 patients with nonmetastatic muscle-invasive bladder cancer treated with curative intent between 2015 and 2025. Thirty-nine received dose-escalated radiotherapy and 68 received standard-dose treatment; median follow-up was 23 months.
- Standard treatment delivered 55 Gy in 20 fractions or 64 Gy in 32 fractions to the whole bladder. Dose escalation used a simultaneous integrated boost to the primary tumour of up to 60 Gy in 20 fractions or 70 Gy in 32 fractions, with a 5 mm boost PTV margin.
- All treatments used VMAT with an empty-bladder protocol and almost universal daily CBCT. Approximately 51% of patients did not receive concurrent chemotherapy, predominantly because of comorbidity or poor performance status.
- The two-year cumulative incidence of invasive bladder recurrence was 5.5% with dose escalation versus 27.5% with standard dosing. After adjustment for T stage, dose escalation remained associated with an 80% lower recurrence risk (subdistribution HR 0.20, 95% CI 0.05–0.89; p = 0.035).
- Dose escalation did not significantly affect non-invasive recurrence: the two-year incidence was 6.7% versus 9.9%, respectively. One of two invasive failures in the escalation group arose within the boost field, while none of its three non-invasive recurrences occurred inside the boosted region.
- Two-year metastasis incidence was 21.1% versus 32.3%, and overall survival was 71.1% versus 64.4%, but neither difference was significant. No dose-escalated patient required cystectomy for invasive recurrence, compared with two patients after standard treatment.
- Grade 2 or greater genitourinary toxicity occurred in 17.9% versus 22.1%, and gastrointestinal toxicity in 5.1% versus 7.4%, with no significant differences. The only two grade 3 events occurred in the standard-dose group.
CLINICAL TAKEAWAY
A tumour-directed simultaneous integrated boost may reduce the clinically important risk of invasive intravesical relapse without increasing early toxicity. The result is not sufficient to establish a new standard because treatment groups were imbalanced, chemotherapy use was inconsistent, follow-up was short, and the extent of resection and carcinoma in situ were not controlled.