Initial experience with oropharynx-targeted radiation therapy for metastatic squamous cell carcinoma of unknown primary of the head and neck.

Metastasis of unknown primary (MUP) is commonly treated with radiation therapy (RT) to the entire mucosal surfaces and bilateral neck nodes (LN). We report outcomes of oropharynx-targeted RT, retropharyngeal nodes (RPN) and bilateral LN in this context.Single-Institution retrospective study of 68 patients. Forty percent were treated with intensity-modulated radiation therapy (IMRT). Fifty-six percent received concurrent chemoradiotherapy (CCRT). The median age was 58 years, 82% were Caucasian, and 75% males. Stage III disease was present in 9%, stage IVA in 75% and IVB in 16%.At a median follow-up of 3.5 years, the actuarial locoregional control was 95.5%. The emergence of primary developed in 1patient (1.5%) and 2patients (3%) failed in the neck. The median time-to-locoregional failure (LRF) was 18 months. Actuarial long-term RT toxicity was grade 1 xerostomia (68%), dysphagia (35%), neck stiffness (15%) and trismus (6%).RT to the oropharynx, RPN, and bilateral neck provides excellent oncological and functional outcomes in MUP in non-Asian patients. Sparing the mucosal surfaces of the nasopharynx, hypopharynx, and larynx seems reasonable without impacting on survival and locoregional control.