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.