What is the risk of mucosal site emergence after involved neck only radiation for HNSCC of unknown primary in modern cohorts? This multicenter retrospective cohort identified 195 patients (66% HPV positive) with HNSCCUP who received adjuvant RT to either the neck and mucosal sites (63%) or the involved side of the neck only (37%). About a third (62%) had N1 or N2a disease, 24% had N2b, and 14% N3 disease. There were major imbalances between cohorts with the mucosal cohort more likely to be HPV positive, receive chemotherapy, and get a higher prescription dose. In addition, just two of the institutions accounted for the majority of involved neck RT. Given these underlying differences, the rate of mucosal emergence was relatively low in both arms (2.7% neck only vs 0.8% mucosal RT). Contralateral neck failure was higher with involved neck RT (5.5% v 0.8%). Not unexpected, toxicity and feeding tube placement was lower with involved neck RT. | Peters, Int J Radiat Oncol Biol Phys 2025
