Clinical Researches Of Magnetic Resonance Diffusion Weighted Imaging In Radiotherapy Of Nasopharyngeal Carcinoma

Predictors for replanning in nasopharyngeal carcinoma patients undergoing intensity-modulated radiation therapy:a prospective observational studyBackgroundNasopharyngeal carcinoma(NPC)is sensitive to radiotherapy and chemotherapy.Intensity modulated radiation(IMRT)is the standard treatment means for NPC,which can reduce radiation toxicity and achieve better local control in patients with NPC.Most NPC patients will experience changes in anatomic structures due to obvious tumor shrinkage and/or weight loss during IMRT,which leads to the drift of anatomical position and affecting the accuracy of target volume deviation in dose distributions.Recently,the importance of replanning during IMRT has received more attention.And it has been proved that replanning during IMRT is essential,especially for patients receiving CRT.Therefore,it is important to determine when and for what types of patients are repeated CT and replanning preferred during IMRT.To address these questions,we conducted a prospective study to assess the dynamic changes in GTV and CTV and parotid gland on weekly repeat CT images during the course of IMRT for loco-regionally advanced NPC patients and investigated the best time to replan,we also studied the related factors could predict the volume reductions and to explore the predictors of the optimal patients who need replaning.MethodsWe recruited 20 patients who were diagnosed as loco-regionally advanced,non-metastatic stage III or IVa NPC and treated with concurrent platinum-based chemoradiotherapy(CRT)using IMRT.After pre-treatment routine enhanced magnetic resonance imaging(MRI)plus diffusion weighted imaging(DWI)scans,patients received weekly plain MRI plus diffusion-weighted imaging(DWI)scans for five consecutive weeks.Then pre-treatment and weekly ADC values were obtained.All patient underwent original enhanced simulation-CT and weekly plain CT scans during the treatment.The first IMRT plan was generated based on the original planning CT scan.The weekly CT imaging were fused with the original simulation CT imaging,and gross tumor volume(GTV),clinical target volume(CTV)and parotid glands were delineated and the target volumes were recorded by one doctor based on the CT-CT imaging fusion and target transplantation.The shrinkage of GTV,CTV and parotid gland volume were observed and compared weekly.Patients’ weight was monitored weekly and body mass index(BMI)was calculated before treatment.And the relationship between GTV shrinkage and pre-treatment tumor mass volume and pre-treatment tumor apparent diffusion coefficients(ADC)value,CTV reduction and pre-treatment tumor mass volume and pre-treatment patient BMI,parotid glands volume shrinkage and pre-treatment tumor mass volume and pre-treatment BMI were calculated with Pearson9 s correlation test.ⅧResultsThe weight loss was observed weekly during chemoradiotherapy(CRT),with median weight loss 7kg,(range,2-12.5kg)compared with pre-treatment.The median pre-treatment patient BMI was 23.6,(range,19-26.5).The volume of GTV and CTV decreased throughout the course of treatment,with mean shrinkage of 36.03ml(range,10.91-98.82ml)and 76.79m1(range,33.94-125.14ml)at treatment completion of 25 fractions,respectively.The percentage of the initial volume,they were 38.4%(range,25.3-50.7%)and 11.8%(range,6.7-18.3%),respectively.Furthermore,in comparison with the previous week,the most obvious GTVs and CTVs reduction occurred at the fourth week,the completion of 20 fractions,in terms of the percentage compared to previous sim-CT imaging.The volume of parotid gland decreased during the course of treatment,with mean shrinkage of 18.55ml(range,8.58-39.4ml)at treatment completion of 5 weeks.The percentage of the initial volume,they were 34.23%(range,]2.4-42.5%).Compared to the previous week,the most obvious parotid reduction occurred at the third and fourth week,the completion of 15 and 20 fractions.The patient weight loss and CTVs reduction are significantly correlated with pre-treatment BMI,(r=0.58,P = 0.012,and r = 0.48,P = 0.046,respectively);However,no significant correlation was observed between CTVs reduction and initial tumor mass.In addition,the shrinkage of GTVs did not correlate significantly with pre-treatment tumor volume(P = 0.65)but negatively correlated with pre-treatment tumor ADC values(r =-0.46,P=0.042).And,the shrinkage of parotid volume correlate significantly with patient pre-treatment BMI(r = 0.50,P = 0.023)and pre-treatment tumor volume(r = 0.48,P ＝0.033).ConclusionsThese data indicated that patients with high pre-treatment BMI are more likely to occur CTVs and parotid reduction and those with low tumor ADCs is more prone GTVs shrinkage during CRT.Pre-treatment BMI and ADC are potential predictive factors for the determination of replanning during IMRT.In addition,our results indicate that the most obvious shrinkage of GTV,CTV and parotid gland volume occurred at the third and fourth week,therefore,we suggest the most appropriate replanning time is after 20 fractions of treatment.The prognostic value of pretreatment tumor apparent diffusion coefficient values in nasopharyngeal carcinomaBackgroundDiffusion-weighted MR imaging(DWI)is a functional imaging technique,it has increasingly contributed to the management of nasopharyngeal carcinoma(NPC)patients in diagnosis and treatment evaluation.Apparent diffusion coefficient(ADC)is the main parameter of DWI,which can reflect the proliferation activity of tumor.In this study,we observed the relationship between pre-treatment tumor ADC values and clinical prognostic factors of NPC and the correlation of long survival,to explore the prognostic significance of ADC in NPC patients.MethodsThis retrospective study included 93 newly diagnosed loco-regionally advanced NPC patients.All patients underwent enhanced MRI and DWI examination before radiotherapy or chemoradiatherapy,tumour ADC values were obtained.Pre-treatment ADC values were determined and compared with patients’ age,gender,smoking status,alcohol intake,tumor volume,pathological type,tumor stage,and nodal stage using Chi square test or linear regression analysis.Overall survival(OS),local relapse-free survival(LRFS),and distant metastasis-free survival(DMFS)were calculated,then survival between low and high ADC groups were calculated with the Kaplan-Meier method,and the differences were compared by using the log-rank test.Multivariate analysis using a Cox proportional hazards model was used to test the independent significance of different factors.ResultsThe mean ADC value for the primary tumors was 0.72 × 10-3 mm2/s(range:0.48-0.97×10-3 mm2/s).There was no significant difference between pre-treatment ADCs and patients’ age,gender,smoking status,alcohol intake,or tumor stage.A significant difference in the ADCs for different N stages(P = 0.022)and correlation with tumor volume(r =-0.26,P = 0.012)were observed.In comparison,the ADC value for type 4(undifferentiated carcinoma)was lower than that for other 3 pathological types.With a median follow-up period of 49 months(range,36-67 months),the median OS period was 46 months(range,5-67 months).The 3-year OS,LRFS,and DMFS rates were 88.2%,93.5%,and 83.9%,respectively.The 5-year OS,LRFS,and DMFS rates were 83.3%,93.3%,and 83.3%.Patients with pretreatment tumor ADC values ≥ 0.72 ×10-3 mm2/s(the high ADC group)exhibited longer OS and LRFS periods compared with tumor ADC values<0.72 × 10-3 mm2/s(the low ADC group),with P value 0.036 and 0.018,respectively.In addition,patients with deaths or recurrences or distant metastasis had significant lower ADC values than those without disease failures,with P values 0.02,0.021 and 0.044,respectively.With multivariate analysis using Cox proportional hazard test,ADCs showed a significant correlation with OS(P =0.0004),LRFS(P = 0.0009),DMFS(P<0.0001),respectively.ConclusionsPre-treatment tumor ADC values can be considered a noninvasive important prognostic parameter for NPC.