Feasibility of Lower Neck Sparing in Postoperative Radiotherapy for Parotid Gland Cancer.

BACKGROUND/AIM: To analyze failure patterns and evaluate the clinical necessity of lower neck irradiation (LNI) during elective neck irradiation (ENI) in patients with parotid gland cancers (PGCs). PATIENTS AND METHODS: Forty patients with PGCs who received postoperative radiotherapy (PORT) following parotidectomy between 2006 and 2024 were included. LNI was defined as the elective inclusion of neck levels III and IV in the irradiated field. The primary endpoint was progression-free survival (PFS), while secondary endpoints included local-regional failure-free survival (LRFFS), distant metastasis-free survival (DMFS), and overall survival (OS). RESULTS: The median follow-up time was 68.7 months. Among the 40 patients, 19 (47.5%) received LNI as part of their PORT. Five-year rates of LRFFS, DMFS, OS, and PFS were 91.2%, 80.2%, 88.7%, and 76.3%, respectively. While LNI showed no significant association with survival outcomes, multivariate analysis confirmed that perineural invasion (PNI) was a significant prognostic factor for PFS [hazard ratio (HR)=5.17, p=0.028], OS (HR=7.97, p=0.017), and DMFS (HR=9.67, p=0.009). The major failure pattern was distant metastasis (N=8). Regional failures were infrequent (5%), involving level II (N=1) and levels Ib, II, and IV (N=1). CONCLUSION: Regional failures in PGC are rare and predominantly confined to the upper neck. Omitting LNI did not compromise regional control. Treatment strategies for PGCs with PNI should focus on the intensification of systemic therapy and close monitoring for distant metastasis.