Comment on “Impact of Dose and Sensitivity Heterogeneity on TCP”

In [1], the authors give “analytical description and numerical simulations of the influence of macroscopic intercell dose variations and intercell sensitivity variations on the probability of controlling a tumour.” The probability of controlling a tumour is defined as the probability that every tumour cell is killed by the radiation treatment. The authors use a model for calculating the probability of killing all tumour cells presented earlier by the same authors [2]. However, it was shown in a comment to that article that the model presented there cannot be applied to conventional radiation therapy [3], because, in a clinical megavoltage Xray radiation field, the kind of variations of absorbed dose assumed in that model does not occur. In a reply to the comment [4], despite expressly treating “macroscopic intercell dose variations,” the authors refer to microdosimetrical energy deposition variations as motivating their assumption of large and statistically independent variations of absorbed dose over distances of a cell diameter; they write the following.