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/CTV-HR 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.