Radiation Therapy After Surgical Resection Improves Outcomes for Patients With Recurrent Pleomorphic Adenoma

Purpose: Pleomorphic adenoma is a benign salivary tumor that may recur multifocally. In case series, the benefit of radiation therapy (RT) for recurrent pleomorphic adenoma remains unclear. We hypothesized that the combination of surgery and adjuvant RT reduces risk of subsequent recurrence compared with surgery alone for recurrent pleomorphic adenoma. Methods and Materials: Patients who received diagnoses of recurrent pleomorphic adenoma between 1980 and 2016 were identified using an institutional pathology database. Medical records were retrospectively reviewed to determine clinical, operative, pathologic, and imaging characteristics. Kaplan-Meier methods were used to estimate local control after surgery, stratified by completeness of resection and receipt of adjuvant RT. The association of variables with risk of subsequent local recurrence was analyzed using Cox proportional hazards model, and variance estimates were calculated to account for multiple recurrences in the same patient. Toxicities were prospectively recorded in a departmental database. Results: A total of 49 patients presented with at least 1 recurrence, of which 28 were managed with surgery alone, and 21 were treated with surgery and RT. The median follow-up time after the initial recurrence was 48 months (range, 6-531 months). There were 35 subsequent recurrences; 34 after surgery alone and only 1 after surgery with RT. On multivariate analysis, adjuvant RT was associated with decreased risk of recurrence (hazard ratio, 0.09; 95% confidence interval, 0.02-0.41, P = .002), whereas increasing number of prior recurrences was associated with increased risk (hazard ratio, 1.23; 95% confidence interval, 1.13-1.35, P < .001). Common toxicities of RT included dermatitis, xerostomia, and mucositis. Conclusions: For patients with recurrent pleomorphic adenoma, the addition of adjuvant RT after surgery is associated with a significant decrease in risk of subsequent tumor recurrence.