Impact of increasing irradiation time on the treatment of prostate cancers

Abstract

This study aimed to investigate the expected impact of intrafraction repair during increasing irradiation times for the treatment of prostate cancers. Lengthy sessions are indeed expected for some advanced irradiation techniques capable to deliver the large fractional doses required by the increased fractionation sensitivity of the prostates. For this purpose, clinically-derived parameters characterizing repair rates and dose response curves for prostate tumors have been used to calculate the expected loss of effectiveness when increasing the irradiation time. The results have shown that treatment sessions lasting more than about 20 to 40 minutes could reduce the probability of biochemical control of prostate tumors by more than 20 to 30 percentage points. These results are in agreement with some observed clinical results and therefore they suggest that treatment durations in prostate radiation therapy should be carefully recorded in order to explicitly account for intrafraction repair, especially when irradiation techniques make use of multiple beams and imaging sessions. Failure to do so might overestimate the expected effectiveness of the treatment and could lead to disappointing clinical results precisely from the demanding treatment modalities expected to increase the therapeutic gain in prostate radiotherapy.