Comparative Effectiveness On The Different Delineative Patterns Of IMRT GTV After Induction Chemotherapy For The Locally Advanced Nasopharyngeal Carcinoma

Background and Objective:The gross tumor volume(GTV)was obviously decreased after induction chemotherapy(IC)for locally advanced nasopharyngeal carcinoma.This study was to comparison the clinical efficacy of different delineative pattrens on GTV after induction chemotherapy.Methods:Retrospective analysis of 202 primary locoregionally advanced nasopharyngeal carcinoma patient’s clinical data from Jiangxi Provincial Tumor Hospital Department of Radiation Oncology from June 2010 to December 2012.All the patients were treated with at least two cycles platimum-induction chemotherapy(IC),followed by radical intensity-modulated radiation therapy(IMRT)with or without conrurrent chemotherapy.Patients was divided into two groups according to the different delineative patterns of GTV after IC :pre-GTV group(delineated GTV according to the primary tumor befor IC)and post-GTV group(delineated GTV according to the residual tumor after IC).Analyzed the whole patients’ survival rate and prognostic factors,the difference of survival and treatment toxcitiy of the two groups was compared.The gross tumor volume of the 10 locally recurrence patients was delineated and named rGTV(relapse gross tumor volume),contrasted the volume relationship between the original GTV,rGTV and CTV1,then distinguish the patterns of recurrence.The overall survival(OS),progression-free survival(PFS),locally relapse-free survival(LRFS),regional relapse-free survival(RRFS),distant metastasis-free survival(DMFS)was analyzed by the Kaplan-Meier method;the differences between groups were compared by using the log-rank test;multivariable analysis were estimated by using the COX proportion model;the difference of the volume parameters before and after IC were compared by using self-paired t test.Statistical significance was defined as P<0.05.Results:The median follow-up time 35 months(range,3-72 months).The 3-year OS、PFS、LRFS、RRFS and DMFS rates of the pre-GTV group and the post-GTV group were 87.2% vs 82.4%,74.9% vs 74.4%,94.0% vs 96.3%,100.0% vs 97.3% and 77.9% vs 77.9% respectively(for all rates,log-rank>0.05).The total 3 years OS,PFS,LRFS,RRFS and DMFS were 83.3%,74.5%,95.8%,97.8% and 95.8%.There were no significance differences of survival rate between the two groups.The toxicities were tolerated during treatment: grade 3-4 mucositis、xerostomia and radiodermatitis were 6.4%、5.4%、5.9%,respectively.By analyzing the local recurrence model,there were three patients relapse in the pre-GTV group,among them,two were out-fieldfailure,another one was in-field-failure;while seven patients with nasopharyngeal recurrent were all of in-field-failure in the post-GTV group.The univariate analysis results showed that the primary LDH was closely related wiht the OS,PFS and DMFS;the EBV-DNA copies after IC and N staging were bound up with the PFS and DMFS.N staging was the significant independent adverse prognostic factors for OS and DMFS.Conclusions:It is feasible that taking the residual tumor after induction chemotherapy as GTV,not only shink the tumor volume but also maintain the excellent locoregional control rate and overall survival rate.