Outcomes of post-operative treatment with concurrent systemic therapy and radiotherapy (RT) in intermediate (INT) risk resected oral cavity squamous cell carcinoma (OCSCC): A multi-institutional collaboration.

Abstract

e17567 Background: Patients (pts) with adverse pathologic factors in resected OCSCC excluding positive surgical margins or extranodal extension represent a group of INT risk disease. Though not standard of care, adjuvant CRT is often used in INT pts. We conducted a multi-institutional study to evaluate factors associated with improved outcomes in INT pts treated with or without chemotherapy. Methods: An IRB-approved collaborative database of patients with primary OCSCC (Stage I-IVB AJCC 7th edition) treated with primary surgical resection between 1/1/2005 and 1/1/2015 with or without adjuvant therapy was established from 6 academic institutions. Pts were categorized by pathologic features and adjuvant therapy. Kaplan Meier curves, log-rank p-values and multivariate analysis (MVA) were used to describe outcomes by treatment including locoregional control (LRC) and disease free survival (DFS). Results: From a total sample size of 1270 patients, 455 INT risk pts were treated with primary surgical resection and adjuvant therapy; 95 received CRT, 274 received RT alone, and 86 received RT without recorded chemotherapy. 49% of pts had perineural invasion (PNI), 24.8% lymphovascular space invasion, 21.5% poorly differentiated histology, 47.3% with pT3/4 disease, and 27.9% with > 2 lymph node positive (LN+). 55.8% of CRT pts were treated with cisplatin. > 2 LN+ was the only significant predictor of LRC (HR 1.49, p= 0.049). PNI and > 2 LN+ were significant predictors of DFS (HR 1.52, p= 0.003 and HR 1.76, p< 0.001). On MVA, after adjusting for > 2 LN+, treatment with cisplatin-RT was borderline significant for LRC (HR 0.52, p= 0.08). 3 year LRC in pts with > 2 LN+ was 84.4% in pts treated with cisplatin-RT compared with 64.9% for RT alone. Conclusions: The addition of cisplatin-based CRT to INT risk pts is controversial but among pts with > 2 LN+ there was a trend toward benefit. This study is limited by small numbers of pts treated with CRT, though these results highlight the need for further investigation in this population to identify INT pts who would benefit from adjuvant therapy intensification.