Preliminary results of a Phase I/II study with pi-meson (pion) treatment for bladder cancer.

Radiation therapy with negative pi-mesons (pions) was administered to 36 patients with bladder cancer. According to a Phase I/II study, doses varied from 3000 to 3600 pion rad. Although only two complete responses were achieved among 8 evaluable patients who had predominantly papillary bladder tumors, more promising results were obtained in 22 evaluable patients who had sessile, invasive carcinomas: 19 bladders were cystoscopically and cytologically cleared of tumor after 6 months. Although the side effects during the ambulatory treatment were minimal or tolerable, a steep dose-response curve for late side effects was observed with severe complications in 7 of 11 patients who received 3600 or more pion rad.