Dosimetric characteristic of intensity modulated radiotherapy for recurrence nasopharyngeal carcinoma

Objective:To report the dosimetric characteristic for locally recurrent nasopharyngeal carcinoma(NPC) treated with intensity modulated radiotherapy(IMRT).Methods:Thirty patients with local-regional recurrence in the nasopharynx were treated with full course IMRT.Seven patients had recurrence in the neck lymph node.According to the 1992 Chinese Fuzhou Staging System,7 patients had stageⅠ,7 stage Ⅱ,4 stage Ⅲ,and 12 stage Ⅳ.Prescription dose was 58.80-78.76 Gy in GTV,with the fractional dose of 2.28Gy (range,2.0-2.92 Gy).Results:The results of treatment plan showed that the median volume of GTV was 37.46cm3(range,14.30-227.52 cm3).The mean dose of covering gross tumor volume (GTV)(D95)in the nasopharynx was 62.56 Gy and the mean volume of (GTV)(V95) was 98.69%.The mean dose of GTV,clinical target volume CTV1 and CTV2 in the targets were 65.82Gy,54.02Gy and 50.20 Gy,respectively.The mean fractional dose of GTV was 2.28 Gy (range,2.0-2.92 Gy).Conclusion:Intensity modulated radiotherapy improves the target volume coverage and decreases the dose of nearby critical normal structure.