High-dose effects in the treatment of carcinoma of the bladder under air and hyperbaric oxygen conditions.

Twenty-seven patients with carcinoma of the bladder were treated at the Glasgow Institute of Radiotherapeutics as part of a national hyperbaric oxygen trial. These patients were treated on a 4 MeV linear accelerator either in air or in 3 atm, absolute, of oxygen, by random selection. Of these patients, one-third were found to have high-dose effects to an extent which necessitated surgery. No association was found between the incidence of high-dose effects and treatment in air or hyperbaric oxygen. The treatment protocol used in all cases was to give an intended modal tumour dose of 6000 rad in 24 fractions in approximately 5 weeks. As all patients had received the same modal dose, there was no apparent reason why some had developed high-dose effects. However, on the basis of a Cumulative Radiation Effect (CRE) analysis of the treatment regimes given, a close correlation was found between the maximum CRE achieved and the occurrence of high-dose effects. Above a threshold level of 1910 reu in the maximum CRE achieved, there was a high incidence and rapid onset of high-dose effects. The reasons for the occurrence of the exceptionally high CRE values found in some patients are discussed. From a review of clinical results of bladder treatments, it is apparent that at a CRE level of 1910 reu, the tumour control rate is still increasing with CRE. It is proposed that by choosing the dose given on any treatment schedule to keep the maximum value of the CRE achieved just below 1910 reu, the greatest probability of cure would be obtained with minimum complication rate.