Patterns of Care and Survival of Adjuvant Radiation for Major Salivary Adenoid Cystic Carcinoma

Objectives/hypothesis: National Cancer Care Network guidelines suggest consideration of adjuvant radiation even for early stage adenoid cystic carcinoma of the salivary glands. We used the National Cancer Data Base (NCDB) to analyze practice patterns and outcomes of postoperative radiotherapy for adenoid cystic carcinomas.

Study Design: Retrospective NCDB review.

Methods: Patients with nonmetastatic adenoid cystic carcinoma of the parotid, submandibular, or another major salivary gland from 2004 to 2012 were identified. Information was collected regarding receipt of postoperative radiation. The Kaplan-Meier method was used to assess overall survival and Cox regression analysis to assess impact of covariates.

Results: There were 1,784 patients included. Median age was 57 years old and median follow up was 47.5 months. Of the patients, 72.4% of underwent partial/total parotidectomy and 73.6% received postoperative radiation. The 5-year survival was 72.5% for those receiving surgery alone compared to 82.4% for those receiving postoperative radiation (P < .001). On subgroup analysis, this survival difference favoring postoperative radiation was significant for pT1-2N0 (P < .001), pT3-4N0 (P = .047), pTanyN+ (P < .001), and for positive margins (P = .001), but not for negative margins (P = .053). On multivariable analysis, postoperative radiation remained associated with improved overall survival (hazard ratio [HR] = 0.63, 95% confidence interval: 0.50-0.80, P < .001). The utilization of intensity modulated radiation therapy (IMRT) increased from 16.9% in 2004 to 56.3% in 2012 (P < .001). There was no survival benefit for IMRT over three-dimensional radiation therapy (HR = 0.84, P = .19).

Conclusions: Postoperative radiation therapy for salivary adenoid cystic carcinoma was associated with improved survival even for those with early-stage disease.

Level Of Evidence: 4 Laryngoscope, 127:2057-2062, 2017.