Hypofractionated radiotherapy for breast cancer: too fast or too much?

Hypofractionated schedules are potentially attractive in the treatment of breast carcinoma (1-9). From radiobiological point of view, the linear quadratic model suggests that when the α/β ratio of the tumor is the same or less than that of the critical normal tissue, then a larger dose per fraction (hypofractionation) with a modest decrease in total dose, may be equally or potentially more effective than conventional fractionation. An estimate of 4 Gy for α/β value has been already reported for the fractionation sensitivity of breast cancer (10). The low estimated α/β ratio for breast cancer means that it is probably as sensitive to fraction size as is dose-limiting normal tissue, and hypofractionation for breast cancers may actually be advantageous. Thus, breast cancer seems a promising field for hypofractionated schedules of irradiation.