Radiation Therapy Oncology Group Phase I-II study on fast neutron teletherapy for carcinoma of the bladder.

From June 1977 through March 1981, the Radiation Therapy Oncology Group sponsored a Phase I-II study (RTOG 77-05) on the use of fast neutrons for treating carcinomas of the urinary bladder. Patients entered on the study had Stage B1 (grade III or IV histology) or Stage B2, C, or D1 (any grade histology) disease. Thirteen patients received preoperative mixed-beam (neutron/photon) irradiation to 50 photon Gy-equivalent, and in 12 of these a cystectomy was performed in 4 to 6 weeks. The incidence of pathologic downstaging to Po was 58% in the cystectomy specimens. The projected survival at 30 months is 32%. Twenty-six patients were treated definitively with mixed-beam irradiation consisting of 50 photon Gy-equivalent to the pelvis followed by a 20 photon Gy-equivalent boost to the bladder itself. Eighteen of 26 patients (69%) achieved tumor clearance at some time during their follow-up but 8/18 (44%) of these ultimately exhibited some component of local failure. The projected survival at 30 months for this group of patients is 34%. However, the subset of patients with Stage B or C disease had a projected survival at 30 months of 60%. Four patients received definitive neutron irradiation alone and 3/4 achieved tumor clearance at some time during their follow-up. Actuarial curves are presented for patient survival and duration of local control, and results are compared with comparably staged patients treated with megavoltage photon irradiation. Treatment-related morbidity is also discussed.