Role of elective neck dissection and adjuvant radiation therapy in patients with polymorphous adenocarcinoma.

Purpose To evaluate the role of elective neck dissection (END) and of adjuvant radiation (aRT) in polymorphous adenocarcinoma (PAC), previously known as polymorphous low-grade adenocarcinoma (PLGA). Methods Retrospective cohort study of patients in the National Cancer Database with a histology of PAC (coded as PLGA) at a head and neck site diagnosed between 2004 and 2015. Multivariable Cox proportional hazard modeling was used to assess overall survival in the overall population, and in sub-analyses of clinically N0 disease, positive resection margins, and late stage disease. Results A total of 922 patients [66.8% female; mean (SD) age, 60.9 (13.9) years] met inclusion criteria. 74.7% of patients received surgery alone, and 18.0% received surgery and aRT. Only 7.6% of patients with clinically N0 disease received an END, with 10.6% of these having at least one positive node. END did not have a survival benefit compared to no END [HR 1.28 (0.61-2.68)]. Compared to surgery alone, aRT did not have significantly increased survival in the overall population or in late stage [HR 0.68 (0.39-1.19) and HR 0.46 (0.18-1.22), respectively]. On sub-analysis of patients with positive resection margins, aRT had a significant survival benefit compared to surgery alone [HR 0.37 (0.14-0.99)]. Conclusion PAC is a rare, slow-growing malignant tumor typically treated with surgical excision, with undefined indications for END or aRT. Our findings show END to not have a benefit to overall survival. In patients with positive resection margins, there was a survival benefit for aRT.