Counting carbs.

Carbon ion treatment has distinct advantages as a heavy particle, many of which are best exploited for head and neck cancers. For more so than with even proton therapy, however, a vastly different relative biological effectiveness (roughly 3.0 as compared to 1.1 with protons) means conventional normal tissue complication probabilities (NTCP) can be thrown out the window. Enter this unique perspective borne from the experience of 187 patients receiving head and neck radiation at a Japanese carbon ion center. The biggest predictors of grade 2-3 dermatitis was the absolute surface area receiving an RBE-weighted dose of either 40 Gy (AUC 0.78) or 20 Gy (AUC 0.77). There were no clear cut-offs for ideal goals; simply less was better. | Li, Int J Radiat Oncol Biol Phys 2022