Feasibility of Selective Neck Irradiation with Lower Elective Radiation Dose in Treating Nasopharynx Cancer Patients

PURPOSE: This study aimed to report the clinical outcomes following selective neck irradiation (SNI) with lower elective radiation therapy (RT) dose in treating nasopharyngeal cancer (NPC) patients. MATERIALS AND METHODS: A total of 347 NPC patients received definitive RT according to our SNI policy and were retrospectively analyzed. The clinical target volumes (CTVs) were subdivided into CTV at high risk (CTV-HR) and CTV at low risk (CTV-LR). The typical doses to gross tumor volume (GTV), CTV-HR, and CTV-LR were 68.4-70.0 Gy, 54.0-60.0 Gy, and 36.0 Gy. RESULTS: With the median follow-up of 68.1 months (range, 2.3 to 197.1 months), the 5-year rates of loco-regional control and progression-free survival in all the patients were 85.0% and 70.8%, respectively. Thirty patients developed regional failure and the regional control rates at 3 and 5 years were 92.6% and 91.4%, respectively. The sites of regional failure in relation to the target volume were exclusively inside GTV/CTV-HR in 20, inside and outside GTV/CTVHR in three, and exclusively outside GTV/CTV-HR in seven, which were 5.7%, 0.9%, and 2.0% of total patients, respectively. CONCLUSION: The clinical outcomes by the current SNI policy were feasible and comparable to those following classic elective nodal irradiation policy.