Response to ionizing radiation of human bladder transitional cell carcinomas grown in the nude mouse.

The sensitivity to ionizing radiation of three human bladder transitional cell carcinomas grown in the nude mouse was investigated at four different radiation levels, 500, 1,000, 2,000 and 4,000 rad. Each tumor line exhibited a response pattern which reflected to a certain degree tumor differentiation and growth rate in the nude mouse. Exposure to 1,000 rad was the minimum amount of radiation required to produce a distinct, although transient, tumor response in all three tumor lines characterized by a growth delay of 3-4 weeks, whereas maximum tumor response was observed at the 4,000 rad radiation level. These studies would permit a better understanding of the behavior of human bladder cancer to ionizing radiation and may further facilitate efforts at identifying effective radiosensitizing agents that may result in maximizing tumor response.