To investigate whether delivering an increased radiation dose to the tumor-bearing region of the bladder alone would improve local disease control without increasing treatment toxicity.

A total of 149 patients with unifocal T2-T3N0M0 bladder carcinoma were randomized between whole bladder conformal radiotherapy (WBRT, 52.5 Gy in 20 fractions, n = 60) and partial bladder conformal RT (PBRT) to tumor alone with 1.5-cm margins within either 4 weeks (PBRT4, 57.5 Gy in 20 fractions, n = 44) or 3 weeks (PBRT3, 55 Gy in 16 fractions, n = 45). The response was assessed cystoscopically after 4 months.

The 5-year overall and CFS rate was 58% and 47%, respectively, for the whole population. The CR rate was 75% for WBRT, 80% for PBRT4, and 71% for PBRT3 (p = 0.6), with a 5-year local control rate of 58%, 59%, and 34%, respectively (p = 0.18). Solitary new tumors arose within the bladder, outside the irradiated volume, in 6 (7%) of 89 patients who underwent PBRT. The 5-year overall survival and cystectomy-free survival rate was 61% and 49% for WBRT, 60% and 50% for PBRT4, and 51% and 41% for PBRT3 (p = 0.81 and p = 0.59). The treatment toxicity was mild and equivalent across the three trial arms.

The reduction in treatment volume allowed delivery of an increased radiation dose without a reduction in local tumor control or the development of excess toxicity. However, this dose-escalated partial bladder approach did not result in significantly improved overall survival.