Association of Postoperative Radiotherapy With Survival in Patients With N1 Oral Cavity and Oropharyngeal Squamous Cell Carcinoma.

Importance: The guidelines for head and neck cancer recommend consideration of adjuvant postoperative radiotherapy (PORT) for patients with pT1N1 or pT2N1 disease in the absence of other adverse features. This recommendation was recently changed for oropharyngeal (OP) squamous cell carcinoma (SCC).

Objective: To examine the use and outcomes of PORT for N1 OP SCC and oral cavity (OC) SCC.

Design, Setting, and Participants: This retrospective cohort study identified 1467 adult patients with OC SCC and 790 patients with OP SCC with pT1N1 or pT2N1 disease in the absence of other adverse features from the National Cancer Database from January 1, 2004, to December 31, 2013. Patients who received adjuvant chemotherapy or palliative radiotherapy or who had adverse pathologic features were excluded. Statistical analysis included χ2 tests and Cox proportional hazards regression analysis. Data were analyzed from November 10, 2015, to June 30, 2016.

Main Outcomes and Measures: Overall survival.

Results: Of the 1467 patients with OC SCC (842 men [57.4%]; 625 women [42.6%]; mean [SD] age, 61.3 [13.8] years), 740 (50.4%) received PORT. Of the 790 patients with OP SCC (584 men [73.9%]; 206 women [26.1%]; mean [SD] age, 58.2 [10.3] years), 449 (56.8%) received PORT. After controlling for patient demographics, pathologic characteristics, and hospital-level variables, PORT was associated with improved overall survival for patients with OC SCC (hazard ratio [HR], 0.76; 95% CI, 0.63-0.92) and OP SCC (HR, 0.62; 95% CI, 0.41-0.92) with pN1 disease without adverse features. On stratified analysis, this association persisted for patients younger than 70 years (OC SCC HR, 0.77; 95% CI, 0.61-0.97; OP SCC HR, 0.48; 95% CI, 0.31-0.75) and those with pT2 disease (OC SCC HR, 0.64; 95% CI, 0.43-0.96; OP SCC HR, 0.56; 95% CI, 0.32-0.95), but there was no association with overall survival among patients 70 years or older (OC SCC HR, 0.78; 95% CI, 0.58-1.06; OP SCC HR, 1.55; 95% CI, 0.63-3.82) and those with pT1 disease (OC SCC HR, 0.80; 95% CI, 0.60-1.07; OP SCC HR, 0.66; 95% CI, 0.35-1.24).

Conclusions and Relevance: PORT may be associated with improved survival in patients with pN1 OC and OP SCC, especially in those younger than 70 years or those with pT2 disease.