IMRT-based treatment of unknown primary malignancy of the head and neck: Outcomes and improved toxicity with decreased mucosal dose and larynx sparing.

BACKGROUND: Radiation therapy for squamous cell cancer of the head and neck with unknown primary (head and neck CUP) has been associated with significant levels of swallowing toxicity. We examined the effect of changes in mucosal dose on development of laryngeal strictures and percutaneous endoscopic gastrostomy (PEG) dependence. METHODS: Retrospective analysis of 58 patients with head and neck CUP treated with intensity-modulated radiation therapy (IMRT) at the Dana Farber Cancer Institute from August 2004 through July 2013. RESULTS: There were no significant differences between any recurrences for groups treated to 56 versus ≥60 Gy to the mucosal surfaces. However, mucosal dose and chemotherapy type were associated with stricture on multivariable analysis; median PEG dependence was decreased for patients treated to 56 Gy. A larynx-sparing approach was associated with improved outcomes for strictures and PEG use. CONCLUSION: In this single institution study, a 56 Gy IMRT-based mucosal dose demonstrated significant improvements in swallowing toxicity. Additional benefit was seen with larynx-sparing IMRT.