Volume of prophylactic irradiation to neck for stage N0 nasopharyngeal carcinoma patients treated with intensity-modulated radiotherapy

Abstract

Objective To investigate the volume of prophylactic irradiation to the neck for stage N0 nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiotherapy (IMRT).Methods Retrospective analysis was performed on the clinical records of 270 patients with stage N0 NPC (based on the 6th version of AJCC/UICC staging system),who underwent IMRT as the initial treatment in our center from 2003 to 2008.Among all the patients,171 received prophylactic upper-neck irradiation,and 99 prophylactic whole-neck irradiation.All of them received 6-MV X-ray IMRT to the primary focus of NPC and the lymphatic drainage area in the upper neck (Levels Ⅱ,Ⅲ,and Ⅴ A lymph nodes) at doses of 68 Gy/30fractions and 54 Gy/30 fractions over 6 weeks.In addition,the patients receiving prophylactic whole-neck irradiation had the lower neck and supraclavicular fossae treated by anterior neck semi-field conventional technique at a dose of 50 Gy/25 fractions.Results The median follow-up was 65.1 months (range 4-106months),and the follow-up rate was 93％.The patients undergoing prophylactic upper-neck irradiation and prophylactic whole-neck irradiation had 5-year disease specific survival rates of 95.3％ and 91.9％ (x2 =0.76,P =0.384),relapse-free survival rates of 99.4％ and 99.0％ (x2 =1.18,P =0.278),and distant metastasis-free survival rates of 98.8％ and 94.9％ (x2 =2.31,P =0.128).The 5-year distant metastasisfree survival rate was significantly higher in patients without retropharyngeal lymph node (RLN) metastasis than in those with RLN metastasis (99.4％ vs.93.7％,x2 =8.96,P =0.003).Grade 1-2 mucositis and pharyngitis were the most common acute adverse reactions in patients.At 24 months after IMRT,no grade 3 or 4 xerostomia and trismus were developed.Conclusions Prophylactic irradiation to the upper neck may be feasible for stage N0 NPC patients treated with IMRT.It is reasonable in the 7th version of AJCC/UICC staging system that NPC with negative cervical lymph nodes and positive RLNs is reclassified to stage N1. Key words: Nasopharyngeal neoplasms / radiotherapy ; Radiotherapy, intensity-modulated ; Prophylactic irradiation to the neck; Prognosis