Adjuvant radiation for salivary gland malignancies is associated with improved survival: A National Cancer Database analysis

Abstract

Objective: There are no randomized data to support the use of postoperative radiation for salivary gland malignancies. This study uses the National Cancer Database (NCDB) to describe the epidemiology of salivary gland cancer patients and to investigate whether treatment with adjuvant radiation improves overall survival. Methods and materials: A total of 8243 patients diagnosed with a major salivary gland cancer were identified from the NCDB. All patients received primary surgical resection of their malignancy. Patients were risk-stratified by adverse features, and overall survival rates were determined. Patients were considered high risk if they had extracapsular extension and/or positive margin after resection. Patients were considered intermediate risk if they did not meet the criteria for high risk but had pT3-T4 disease, pN+ disease, lymphovascular space invasion, adenoid cystic histology, or grade 2-3 disease. Patients who did not meet criteria for high or intermediate risk were considered low risk. Overall patient demographics, disease characteristics, treatment factors, and outcomes were summarized with descriptive statistics and analyzed with STATA. Results: Median follow-up in this cohort was 42.4 months, with the median age of 58 years. Patients in the high-risk group had greater survival (hazard ratio [HR], 0.76; P = .002; 95% confidence interval [CI], 0.64-0.91) if they received adjuvant radiation therapy. In contrast, patients in the intermediate- (HR, 1.01; P = .904; 95% CI, 0.85-1.20) and low-risk groups (HR, 0.85; P = .427; 95% CI, 0.57-1.26) did not experience a survival benefit with adjuvant radiation therapy. Conclusions: This large analysis compared survival outcomes between observation and adjuvant radiation alone in risk-stratified patients after resection of major salivary glands using a national database. The use of adjuvant radiation for high-risk major salivary gland cancers appears to offer a survival benefit. Although an overall survival benefit was not seen in low- and intermediate-risk salivary gland cancers, this study could not address impact on local control because of the limitations of the NCDB.