Role of Postoperative Radiotherapy in Nonmetastatic Head and Neck Adenoid Cystic Carcinoma

Abstract

Background: Head and neck adenoid cystic carcinoma (ACC) is a rare malignant tumor that is prone to local recurrence. The NCCN Guidelines for Head and Neck Cancers recommend that all patients with ACC receive postoperative radiotherapy (PORT). However, whether PORT can improve local control and which patients can benefit from PORT are unknown. This study aimed to assess the role of PORT and provide individualized suggestions for postoperative therapy in patients with ACC. Patients and Methods: We retrospectively reviewed patients with nonmetastatic head and neck ACC who underwent surgery with or without PORT. Recursive partitioning analysis (RPA) was performed to categorize the patients and predict local recurrence-free survival (LRFS). The survival outcome was compared between non-PORT and PORT groups. Results: A total of 319 patients were included. PORT was identified as a prognostic factor for LRFS in univariate (P=.01) and multivariate analysis (P<.01). However, it did not improve distant metastasis-free survival, disease-free survival, or overall survival in univariate analysis. RPA categorized patients into 3 prognostic groups: low-risk (negative margin, T1–T2, primary location = major or minor salivary gland), intermediate-risk (negative margin, T1–T2, primary location = other locations instead of a major or minor salivary gland; negative margin, T3–T4; positive margin, without bone invasion), and high-risk (positive margin, with bone invasion). Significant LRFS improvements in the PORT group were observed among intermediate-risk (P<.01) and high-risk patients (P<.05). LRFS improvements among low-risk patients were relatively insignificant (P=.10). Conclusions: PORT was shown to be a positive prognostic factor for improved LRFS in ACC. Furthermore, PORT could significantly improve LRFS in intermediate-risk and high-risk patients with ACC, but whether low-risk patients could benefit from PORT needs further study.