The Dose-volume And Clinic Characters Of The Nasopharyngeal Carcinoma Patient Diagnosised With Radiation Induced Temporal Lobe Necrosis After Intensity-modulated Radiotherapy

ObjectiveThis retrospective study aim to explore the relationship betweenradiation induced temporal lobe necrosis (RITLN) and the dose-volumeand clinical characteristics of temporal lobe after intensity-modulated radiation therapy (IMRT) which could provide accuratetemporal lobe restrict dose and corresponding volume. To explore theRITLN occurrence regularity and the tolerance dose of temporal lobewas included in this study. Besides，explore the clinic effect ofadaptive radiation therapy（ART） to reduce RITLN incidence.MethodsCollect the patients of Sichuan cancer hospital from January,2004to January,2009that primary diagnosised with nasopharyngeal carcinoma and whole course treated by IMRT，a total of695patientsin our study. RITLN was diagnosised with magnetic resonance imaging(MRI)。in this study we were collected to analysis the temporal lobedose-volume, general situation(such as Gender, year, T stage,diabetes, hypertension, lipid levels,drinking and smoking history)andtreatment ituation (chemoradiotherapy and targete therapy).Analysisthe D0.1cc(the0.1cubic centimeter temporal lobe which received themax dose), D0.5cc, D1cc, D2cc, D3cc, D5cc,10cc, D15cc, D20cc,Dmean（mean dose）, Dmax （maximum dose）of bilateral temporal lobe. Thenanalysis the relationship between RITLN and the dose of temporal lobeand necrosis region. Select which dose-volume parameter andcorresponding dose could predict RITLN. At last, analysis the RITLNindependent impact factors in whole factors such as temporal lobedose-volume, general situation and treatment situation.ResultA total of59patients diagnosised with RITLN in695patients.Thedose of necrosis temporal lobe significant exceed the normal temporallobe(（p <0.05). The necrosis region all located in high dose regionin primary plan. ROC curve analysis show that the area under curveincreased firstly and then decreased with the increase in volume oftemporal lobe and D2cc has the maximum area under curve in abovedose-volume parameters and it was an independent risk factor inMultivariate analysis. The incidence of RITLN Rising exponentially along with the increase of dose within a certain range. The RITLNincidence less than5%in5years(TD5/5，Tolerance dose) when D2ccless than61.97Gy（95%CI：60.74，63.19） and the incidence less than50%in5years(TD50/5) When D2cc less than73.26Gy（95%CI：71.98，74.46）. The RITLN biological effective dose TD5/5was D2cc less than60.31Gy（95%CI：59.09，61.54）,TD50/5was76.85Gy（95%CI：75.74，78.22）.The dose of patients with locally advanced nasopharyngealcarcinoma using single plan and multi-plans：The temporal lobe doseof T3stage patients with single plan and multi-plan were67.1±7.2Gy and62.3±6.6Gy, P=0.000，The dose of T4stage patients withsingle plan and multi-plan were69.4±7.7Gy and65.5±6.9Gy，P=0.001. T3stage patients RITLN incidence with single plan andmulti-plan were13.7%and5.8%, P=0.037. T3stage patients RITLNincidence with single plan and multi-plan were21.8%and11.7%,P=0.038.The5years local control rates with single plan andmulti-plan:T3phase5year local control rates were94.5%and94.3%,P=0.933，T4phase5year local control rates were92.1%and93.2%，P=0.78。In univariate analysis，T stage（P=0.000）,temporal lobe dose（P=0.000）, concurrent chemotherapy concurrent chemotherapyconcurrent chemotherapy concurrent chemotherapy （P=0.002）,diabetes（P=0.027）, single dose is≥2Gy （P=0.000）and number of plan P=0.036）have statistical significance. T stage(P=0.000）,temporal lobe dose（P=0.000）, concurrent chemotherapy（P=0.009）,single dose is≥2Gy（P=0.008）and number of plan（P=0.021）werethe independent risk factors in Multivariate analysis, odds ratio was3.463,4.023,3.963,2.976and0.339.ConclusionThe incidence of radiation induced temporal lobe necrosis has closelyrelated to the dose of temporal lobe and corresponding volume. RITLNmainly due to temporal lobe received high radiation dose, the restrictdose（BED）of temporal lobe was D2cc less than60.31Gy. adaptive radiationtherapy could reduce the temporal dose and incidence of RITLN in locallyadvanced nasopharyngeal carcinoma patients. Besides，T stage, concurrentchemotherapy（P=0.009）, single dose is≥2Gy were the independent riskfactors of RITLN.