In select clinical scenarios of well-lateralized tumors, radiotherapy can be delivered to the primary tumor or tumor bed and the ipsilateral nodal regions. This review article evaluated the current evidence supporting the use of proton beam therapy in unilateral irradiation of head and neck cancers including salivary tumors, cutaneous malignancies, skull base perineural invasion, periorbital tumors, oropharyngeal cancer and reirradiation.

This review found that both prospectively collected single-arm studies and retrospective comparative analyses now demonstrate compelling reductions in acute toxicities in favor of PBT. Some studies demonstrate impressively low rates of chronic toxicities for optic and orbital structures and a safer path to organ preservation without compromising tumor control rates. Several randomized studies are currently active to confirm the reduction in acute toxicities and quantify the possible differences in chronic toxicities.