Preliminary results of a phase I/II study With Pi-Meson (Pion) treatment for bladder cancer

Abstract

Radiation therapy with negative pi-mesons (pions) was administered to 36 patients with bladder cancer. According to a Phase 1/11 study, doses varied from 3OOO 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 evduable 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. Densely ionizing radiation from heavy charged particles, such as certain ions (carbon, neon, argon) or negative pi-mesons (pions), is theoretically more advantageous because of particular physical properties; the maximum of energy is released only at the end of the particle range (Bragg peak), within a few centimeters (Fig. 1). Furthermore, high linear energy transfer (LET) particles in the stopping region reduce variations in cell-cycle radiosensitivity and enhance damage to hypoxic tumor cells more than low LET (x-ray and gamma ray) radiation.' Compared with uncharged heavy particles (neutrons), pions have (because of their negative electric charge) excellent dosedistribution characteristics. This makes it possible to design a well-defined volume of irradiation around the tumor and to reduce irradiation effects in the surrounding

Urination Frequency and Cystic Pressure Resistance After Fractionated whole or Partial Irradiation of the Rabbit Urinary Bladder

“…1,2). The advantage of such a treatment would mainly be a reduction of the healthy tissue target volume, for example by application of dynamic spot scan techniques in irradiation of bladder carcinomas (3).…”