Positive Surgical Margins in Submandibular Malignancies: Facility and Practice Variation

Objectives: Identify positive margin rate in a national cohort of patients with submandibular carcinoma, identify predictors of positive margins, and associate margins with overall survival.

Study design: Retrospective cohort.

Setting: Commission on Cancer-accredited hospitals.

Subjects and methods: We included patients in the National Cancer Database from 2004 to 2014 who were diagnosed with submandibular carcinoma and underwent primary surgical resection. We determined the rate of positive surgical margins and associated patient, tumor, and treatment factors with positive margins via univariable and multivariable logistic regression analysis. We associated margin status with overall survival by Kaplan-Meier curve and Cox proportional hazards regression.

Results: We identified 1150 patients with submandibular malignancy undergoing surgical resection. Positive margin rate was 41.0%. Increased odds of positive margins were seen in patients with advanced T stage (vs T1, T3: odds ratio [OR] = 3.04, P < .001; T4a: OR = 2.89, P < .001), adenoid cystic carcinoma histology (OR = 1.54, P = .020), and those treated at nonacademic facilities (OR = 1.41, P = .008). Patients who underwent a preoperative diagnostic biopsy had decreased odds of positive margins (OR = 0.72, P = .014). Positive margins were associated with reduced overall survival (58% vs 69% 5-year overall survival, P < .001; hazard ratio = 1.49, P = .001) when controlling for patient, tumor, and management factors.

Conclusions: The national positive margin rate of submandibular carcinoma is 41.0%. Preoperative biopsy and treatment at academic institutions independently decreased the risk of positive margins, and positive margins were independently associated with diminished overall survival. Positive margin rate for submandibular carcinoma may be considered a benchmark for quality of care.