Helical tomotherapy as a means of administering total or partial scalp irradiation: In regards to Bedford et al. (Int J Radiat Oncol Biol Phys 2005;62:1549-1558).

摘要

Bedford et al. (1) recently described an effective step-and-shoot intensity-modulated radiotherapy (IMRT) method of irradiating extensive areas of the scalp. Their positive results contrast with those of Locke et al. (2), who found nontarget dose to be unacceptable with serial tomotherapy. The authors admit that the differences might exist in partbecause they addressed partial, unilateral scalp lesions, whereas Locke et al. evaluated total scalp irradiation. We recently described an approach that works well for unilateral or total scalp irradiation (3). Helical tomotherapyseems to be well suited for scalp irradiation because it can deliver radiation tangentially to every point on the scalp, eliminates the complexities of matching abutting fields, and avoids the need for more than one modality (i.e., electrons/photons). In addition, the megavoltage computed tomography (CT) verifies setup simultaneously in three dimensions rather than two; the skull is a reliable, easily delineated landmark for each fraction. We found that bolus (and the accompanying uncertainties) is not required when using shallow, tangential, fully circumferential irradiation. In our comparison, our method produced better dose-volume histograms and isodose curves than the Akazawa photon/electron technique or concentric electron beams. In addition, total scalp dose homogeneity and equivalent uniform dose was superior. The brain dose above 30 Gy was reduced up to 66%. Overall, we believe that the dose-volume histograms obtained were comparable or perhaps superior to those presented by Bedford et al., despite addressing the entire scalp.