Primary vs nodal site PET/CT response as a prognostic marker in oropharyngeal squamous cell carcinoma treated with intensity-modulated radiation therapy.

Abstract

Positron emission tomography/computed tomography (PET/CT) in staging of advanced oropharyngeal squamous cell carcinoma (OPSCC) and at 3 months posttreatment (PETpost) is often utilized to assess response. The significance of lymph node vs primary site treatment response is incompletely understood. We reviewed 230 patients treated with radiation therapy. PETpost response was graded at primary and nodal sites and correlated with survival. Median age was 58, and 83% were p16-positive. Median follow-up was 24.3 months. Nodal response at PETpost predicted improved 2-year local recurrence-free survival (LRFS) (93% vs 72%, P =.004), 2-year disease-free survival (DFS) (80% vs 61.3%, P =.021), and 2-year overall survival (OS) (89% vs 83%, P =.051), while primary response only predicted improved 2-year LRFS (91% vs 76% P = .035). In OPSCC patients, both nodal and primary response at 3 months on PET/CT predicted for improved LRFS, but only nodal response predicted DFS and OS.