Inhibition by Proton Irradiation on the Development of Invasive Bladder Carcinomas Induced by N-Butyl-N-(4-Hydroxybutyl) Nitrosamine in Mice

Abstract

Fifty-five female C3H/He mice were given 0.05% N-bytyl-N-(4-hydroxybutyl) nitrosamine in their drinking water for 18 weeks. In week 19, eleven mice (group 3) were sacrificed to confirm that they all had bladder carcinoma. The remaining mice were divided into two groups. Group 1 received 20 Gy of proton irradiation over the whole pelvis, while group 2 received no treatment as a control. After 3 weeks all the animals were sacrificed and their bladders were resected to weigh and to examine histologically. The average weight of the bladder, as an index of the tumor volume, was 67.7 mg in group 1, 120.6 mg in group 2 and 106.5 mg in group 3. There was a significant differences (p<0.05) between group 1 and group 2. The incidences of superficial (pT1) and deeply invasive (pT2–3) bladder carcinomas were [10/18 (56%) and 8/18 (39%)] in group 1, [3/17 (18%) and 14/17 (82%)] in group 2 and [2/11 (18%) and 9/11 (82%)] in group 3, respectively. These rates of incidence were significantly different (p<0.05) between group 1 and group 2. However, there was no significant difference (p=0.068) between group 1 and group 3. These results indicate that proton irradiation is effective for treatment of invasive bladder carcinoma in mice. © 1991, THE JAPANESE UROLOGICAL ASSOCIATION. All rights reserved.