Reirradiation of Recurrent and Second Primary Cancers of the Head and Neck: a Review of the Contemporary Evidence.

Recurrent and second primary head and neck cancers represent a clinical challenge due to frequently unresectable and/or locally advanced disease. Given that many of these patients have received definitive doses of radiation previously, reirradiation is associated with significant morbidity. Use of modern approaches such as conformal photon-based planning and charged particle therapy using protons or carbon ions allows for greater sparing of normal tissues while maintaining or escalating doses to tumor volumes. While the reirradiation data has consistently shown benefits to local control and even survival from escalation of radiotherapy dose, excessive cumulative doses can result in severe toxicities, including fatal carotid blowout syndrome. For all modalities, appropriate patient selection is of utmost importance. Large-scale trials and multi-institutional registry data are needed to standardize treatment modalities, and to determine optimal doses and volumes for reirradiation.