ABSTRACT
Objective To investigate the benefits of replanning after induction chemotherapy(IC) by analyzing the dosimetric impact of IC on intensity-modulated radiotherapy(IMRT)for locally advanced nasopharyngeal carcinoma(NPC)and the dosimetric characteristics of replanning after IC, and to provide data for the rational design of clinical radiotherapy plans. Methods 16 NPC patients underwent contrast-enhanced CT scan once before and after IC.Target volumes were delineated and the chemotherapy plans were created,defined as Plan-1 and Plan-2,respectively. Then the target structure after IC was copied to Plan-1, generating the third plan, defined as Plan-1-2. The paired t-test was used to compare the dosimetric parameters between Plan-1 and Plan-1-2 and between Plan-2 and Plan-1-2. Results Plan-1 vs. Plan-1-2:Plan-1-2 showed significantly reduced D meanof target volume compared with Plan-1(P<0.05). Plan-1-2 significantly increased D meanand D maxof the spinal cord(P<0.05),although significantly reduced D mean of the brain stem and D maxof the temporal lobes compared with Plan-1. Plan-1-2 also had significantly reduced conformity index(CI)and significantly increased homogeneity index(HI)for the target volume compared with Plan-1(P<0.05). Plan-2 vs. Plan-1-2:Compared with Plan-1-2, Plan-2 significantly increased D meanand D minof gross tumor volume(GTV)and primary GTV(P<0.05)and significantly reduced D meanof the temporal lobes and D maxand D meanof the spinal cord(P<0.05), with D max decreased to 430.48 cGy;Plan-2 had significantly increased CI and significantly reduced HI for the target volume compared with Plan-1-2(all P<0.05). Conclusions IMRT plan-1 after IC has worse dosimetric distribution,while replanning after IC has more dosimetric benefits.
ABSTRACT
Objective To investigate the value of induction chemotherapy in the treatment of stage N2.3M0 nasopharyngeal carcinoma with plasma Epstein-Barr virus (EBV) DNA＞4000 copies/ml.Methods A retrospective study was performed on clinical data from 210 patients with stage N2-3M0 nasopharyngeal carcinoma and plasma EBV DNA＞4000 copies/ml who were admitted to our hospital from 2009 to 2013.In the 210 patients,101 received induction chemotherapy plus concurrent chemoradiotherapy (NCRT) and 109 concurrent chemoradiotherapy alone (CCRT).The survival rates were calculated by the Kaplan-Meier method.The log-rank test was used for the analysis of survival rates and univariate analysis of the impacts of the changes in the plasma EBV DNA level after induction chemotherapy on the prognosis.Results The 3-year sample size was 154.The NCRT group had significantly higher 3-year disease-free survival (DFS) and distant metastasis-free survival (DMFS) rates than the CCRT group (80.1％ vs.70.6％,P =0.029;87.1％ vs.76.0％,P=O.036),while there was no significant difference in 3-year overall survival (OS) rate between the two groups (88.0％ vs.80.4％,P =0.210).Patients with stage N2 disease in the NCRT group had significantly higher 3-year DFS and DMFS rates than those in the CCRT group (P=O.031,O.014).Patients with stage N3 disease in the NCRT group had significantly higher 3-year OS,DFS,and DMFS rates than those in the CCRT group (P=0.029,0.012,0.019).In all the patients,the 3-year OS and DMFS rates were improved with the increase in the cycle number of induction chemotherapy (P =0.020,0.021).In the NCRT group,patients treated with 2,3,and 4 cycles of induction chemotherapy before radiotherapy had plasma EBV-DNA clearance rates of 51.85％,76.92％,and 88.57％,respectively (P=0.004).Using the complete clearance of plasma EBV-DNA as a predictor of progression,the sensitivity for the above three groups was 62.50％,66.67％ and 75.00 (P=0.910),respectively,and the specificity was 57.89％,90.00％ and 96.77％ (P=0.000),respectively.Conclusions In the treatment of nasopharyngealcarcinoma with plasma EBV DNA ＞ 4 000 copies/m1,induction chemotherapy improves DFS and DMFS inpatients with stage N2-3 M0 disease and OS in patients with stage N3 disease;induction chemotherapy dose not improve recurrence-free survival rate.The prognosis and plasma EBV DNA clearance rate are improved with the increase in the cycle number of induction chemotherapy.Using the complete clearance of plasma EBV DNA as a predictor of progression,the sensitivity and specificity in patients treated with 4 cycles of chemotherapy are superior over those in patients treated with 2 or 3 cycles of chemotherapy.
ABSTRACT
As induction chemotherapy goes on,target volume,dose distribution in the surrounding organs at risk (OARs),and target dose conformity all change.Therefore,the question is how to develop reasonable radiotherapy plans in clinical practice.Induction chemotherapy followed by radiotherapy is commonly used around the world,but it is recommended to delineate the target volume based on the gross tumor volume before induction chemotherapy and not to reduce the dose.This point of view lacks the basis of evidence-based medicine.The experts and scholars in China clarify the advantages of radiotherapy plans after induction chemotherapy from the aspects of reducing the target volume,reducing the volume of high-dose region in the target volume,increasing the uniform dose coverage in target volume,reducing dose to OARs,and increasing dose conformity.However,at present,there are no objective data on its long-term efficacy and benefit.Besides,no consensus has been reached on how to delineate the target volume and determine the dose distribution after induction chemotherapy,and further studies are needed.