| Background and Objective:This study was to investigate the impact of changing gross tumor volume delineation on the dose distribution after neo-adjuvant chemotherapy.Methods:From January 2009 to December 2010,7 patients with locoregionally advanced NPC were treated with TP regiment neo-adjuvant chemotherapy followed by IMRT with concurrent chemotherapy. We delineated GTV, CTV and PTV according to the gross tumor volume after neo-adjuvant chemotherapy which CTV60 must contain GTV before neo-adjuvant chemotherapy(GTVp). At the same time, we observed the clinical treatment outcome and toxicities of all patients.Results:The post-neoadjuvant chemotherapy GTV was significantly smaller than the pre-neoadjuvant chemotherapy GTV(primary GTV 19.1 cm3 vs 38.9 cm3,P=0.001),the mean decrease of the GTV was 44%. The mean dose of the PTV before and after neoadjuvant chemotherapy was not significantly different (P> 0.05).The PTV70 conformal index(CI) and homogeneity index(HI)were also not significantly different (P=0.3 and P=0.5).The complete response rate was 85% three month after radiotherapy. The one year locoregional control rate was 85.7% and only one patient presented lymph recurrence 13 months after treatment. The toxicities of neoadjuvant chemotherapy followed by IMRT with concurrent chemotherapy were similar to that of IMRT with concurrent chemotherapy alone.Conclusions:Neo-adjuvant chemotherapy by TF could reduce the gross tumor volume. The delineation of GTV according to the post-chemotherapy tumor volume and giving 60Gy to the shrinking region involved by tumor before chemotherapy could reduce the high dose volume. Concurrent chemo-radiotherapy by IMRT following neo-adjuvant chemotherapy has good short-term tumor control, without significantly increasing the toxicities compared with the concurrent chemo-radiotherapy alone. |
