HSR19-092: Adjuvant Radiotherapy Is Associated with Improved Overall Survival for Resected Alveolar Ridge Squamous Cell Carcinoma With Adverse Pathologic Features

Abstract

Background: Alveolar ridge (AR) squamous cell carcinoma (SCC) is poorly represented on prospective clinical trials. Adjuvant management is extrapolated from more common head and neck SCC, including those with a stronger influence from the human papillomavirus. The objective of this analysis is to determine the association between adjuvant radiotherapy (RT) and overall survival (OS) for resected ARSCC based on adverse pathologic features. Methods: Adult subjects in the National Cancer Database diagnosed with invasive nonmetastatic ARSCC between 2010–2014 were identified. Exclusion criteria included prior malignancy, no/unknown surgery, unknown receipt of RT, RT dose <50 Gy or >80 Gy, RT fractions >68, T1–2N0 disease without identifiable NCCN-defined risk factors (positive margin, lymphovascular invasion, pT3–4, N2–3, extranodal extension, or level IV/V nodal metastasis), and unknown/missing NCCN risk factor data. Log-rank test stratified by RT and Cox regression analyses with respect to OS were performed. Results: 1,450 subjects met inclusion criteria, of which 825 (57%) received RT. Median follow-up was 27 months. Adjuvant RT was associated with improved OS (72% vs 65% at 2 years, log-rank P=.004). Stratified by number of NCCN-defined risk factors, adjuvant RT was associated with improved OS for subjects with 2 (74% vs 58% at 2 years, log-rank P<.001) and ≥3 (54% vs 29% at 2 years, log-rank P<.001) risk factors. Adjuvant RT was significantly associated with improved OS on univariate (HR, 0.80; 95% CI, 0.68–0.94; P=.008) and multivariate (HR, 0.72; 95% CI, 0.60–0.87; P=.001) analyses, the latter adjusted for age, comorbidity score, and adverse pathologic features. Each NCCN-defined risk factor, high tumor grade, primary tumor ≥3 cm, and ≥5% nodal positivity (number of pathologic nodes positive among nodes resected) were significantly associated with worse OS on univariate and multivariate analyses. Conclusions: Adjuvant RT for resected ARSCC with adverse pathologic features is associated with significantly improved OS. Subjects with a primary tumor ≥3 cm, high tumor grade, and ≥5% nodal positivity in addition to the NCCN-defined risk factors should be considered for adjuvant RT.