A clinical study aimed at determining the maximum tolerated tumor-focused dose (MTD) for the radical treatment of muscle-invasive bladder cancer using image-guided adaptive radiation therapy has concluded. The study involved 59 patients with T2 to T4aN0M0 unifocal urothelial muscle-invasive bladder cancer, suitable for daily radical radiation therapy. The uninvolved bladder was planned to receive 52 Gy in 32 fractions, while the bladder tumor was targeted with doses of 68, 70, 72, or 74 Gy, adjusted based on organ at risk dose constraints.
Results showed that the MTD was 70 Gy, with acute genito-urinary and gastro-intestinal G3 acute toxicity observed in 19% and 7% of patients, respectively. No acute G4 genito-urinary or gastro-intestinal toxicity was reported. Late toxicity G3 and G4 was seen in 14% and 2% of patients, respectively. The study reported a 5-year overall survival rate of 58% (95% CI, 44%-71%) and a bladder preservation rate of 89% (95% CI, 88%-96%), with 6 patients not retaining native bladder function.
The study concludes that bladder tumor-focused dose escalation to 70 Gy using image-guided adaptive radiation therapy is feasible with acceptable toxicity. This dose level is being further evaluated in a phase II randomized control trial (RAIDER NCT02447549).
