Delineation of the clinical target volume in early-stage nasopharyngeal carcinoma

Abstract

Objective To analyze the clinical outcome and recurrence patterns of IMRT in early-stage NPC,and to explore the rationality of the delineation of clinical target volume (CTV).Methods Totally 124 patients with untreated stage Ⅰ-Ⅱ b NPC received IMRT.CTV was divided into CTV1 and CTV2 according to the biological behavior and characteristics of early-stage NPC,the anatomic location and adjacent of gross tumor volume of nasopharynx and neck lymph node (GTVnx and GTVnd).The prescribed dose of GTVnx,GTVnd,CTV1 and CTV2 was 68 Gy/30 f,60-66 Gy/30 f,60 Gy/30 f and 50-54 Gy/30 f,respectively.To analyze the relationship between recurrence and target volume,and the recurrence patterns,the local and regional recurrence-free survival rates were determined by the method of Kaplan and Meier.The incidence of acute and late toxicity was recorded.Results With a median followup of 111.4 months,2 patients developed local recurrence within GTVnx.Both were in-field recurrence.3 patients had regional recurrence within CTV2,with 2 marginal recurrences,1 outside recurrence.The 5-year local and regional recurrence-free survival rates were 98.4％ and 98.3％,respectively.The overall survival rate was 94.3％.No grade 4 acute or late radiotherapy-related toxicities were observed.The incidence of grade 3 acute or late toxicities was 9.7％ and 4.8％.Conclusions The delineation of CTV in early stage NPC is reasonable with high local and regional control rate,lower marginal and outside recurrence rate,and mild acute or late toxicities.The accuracy of clinical target volume need further study. Key words: Early stage nasopharyngeal carcinoma; Intensity-modulated radiation therapy; Clinical target volume