A Comment on Qi et al.: An Estimation of Radiobiological Parameters for Head-and-Neck and the Clinical Implications. Cancers, 2012, 4, 566-580

Important results were shown as cell survival points in the two panels of the figure which is reproduced in this Comment letter. A curve was fitted assuming the mono-exponential recovery half-time of 17 ± 21 minutes. The wide error limits indicate that this fit is not very good, but the notable feature of both panels is that the last four points are clearly continuing to rise, above the "fitted" curve. This indicates that there is a second, slower, component of repair or recovery and this Comment explores constructively the implications of that additional discovery.