Dose Rate Variations and Cellular Biological Effects in Tumor Control Probability for Head and Neck Cancers

In radiotherapy, tumor control probability (TCP) is the probability of successfully eliminating tumor cells. The TCP value is influenced by factors such as fractionation and various cellular and biological processes. This includes repopulation, repair, redistribution, and reoxygenation. These biological effects on TCP are determined by the dose rate function, particularly in relation to sub-lethal damage, as described by the Lea-Catcheside function. In this paper, two variations of the Lea-Catcheside function were considered: one assuming a constant dose rate and the other based on an exponential fit dose rate function. The results demonstrated that the two variations in dose rate had a minimal impact on TCP values when assessing the biological effects of head and neck cancers. We also considered each biological effect on the TCP. The results showed that repair and repopulation processes prevent the complete elimination of tumor cells, while resensitization effects, such as reoxygenation and redistribution, enhance tumor cell death.