To analyze patterns of care in radiotherapy field design for patients treated for head and neck squamous cell carcinoma of unknown primary origin in the modern era.

From January 2014 to April 2018, 33 patients were treated by intensity-modulated radiation therapy for squamous cell carcinoma metastatic to the cervical lymph nodes of unknown primary origin. A total of 17 patients (52%) were treated by primary radiation; 16 (48%) were treated after surgery. N-classification was N1 (3 patients); N2a (8 patients); N2b (15 patients); N2c (2 patients); and N3 (5 patients). Human papillomavirus status was positive in 19 (58%) and negative in 14 patients (42%).

A total of 15 patients (46%) were treated with classic comprehensive fields to the entirety of the pharyngeal mucosal axis and bilateral cervical necks. Seven patients (21%) received ipsilateral neck radiation only. The total mucosal axis was irradiated in 15 patients (46%). Among the entire population, the nasopharynx and larynx were intentionally omitted in 36% and 48%, respectively. None of the clinical parameters predicted for the use of less-than-comprehensive radiation fields (P > 0.05, for all).

Significant variation exists in the radiotherapeutic management of head and neck unknown primary cancer. Further research to better optimize standards is required.