Reduced Dose and Selective Neck Irradiation Policy in Treating Oropharynx Cancer: Excellent Oncological Outcomes with Very Low Risk of Locoregional Failure

초록

Purpose This study aimed to evaluate the risk of locoregional failure after reduced dose selective neck irradiation (RD-SNI) in Materials and Methods Between 2008 and 2022, 342 OPC patients underwent definitive radiation therapy (with or without concurrent systemic therapy). The doses of 67.2-68.4 Gy to gross tumor volume (GTV), 56-60 Gy to high-risk clinical target volumes (CTVHR), and 32-36 Gy to low-risk clinical target volumes (CTV-LR) were irradiated. The same target delineation and dosing policy were applied to all patients regardless of human papillomavirus (HPV) status. Oncological outcomes including failure patterns were also investigated. Results With a median follow-up of 60.3 months (range, 1.4 to 196.6 months), the 3- and 5-year locoregional control, distant metastasis-free survival, disease-free survival, and overall survival rates were 91.6%/90.7%, 83.7%/80.7%, 78.7%/74.8%, and 91.0%/85.8%, respectively. The HPV-positive patients exhibited significantly better outcomes. Treatment failure occurred in 61 patients (17.8%); 37 (10.8%) had distant metastasis, 22 (6.4%) had local failure, and eight (2.3%) had regional failure. GTV failure was significantly more common in HPV-negative patients (p=0.003). Among the 27 patients with locoregional failure, either GTV and/ or CTV-HR failure occurred in 22 (81.5%), with CTV-LR failure in one (3.7%), and out-target regional (OTR) failure in five (18.5%). Only five failures (1.5%) could be attributed to the current RD-SNI policy: one CTV-LR failure (0.3%) reflecting the RD policy and four OTR failures (1.2%) reflecting the SNI policy. Conclusion Excellent oncological outcomes were achieved with the current RD-SNI policy.

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