Clinical Study Of The Necessity Of Multiple Replanning During The Course Of Intensity-modulated Radiotherapy For Patients With Nasopharyngeal Carcinoma

Background: Nasopharyngeal carcinoma is one of the common head andneck cancer in China and Southeast Asia.Intensity modulated radiationtherapy become the primary means of treatment.Studies have pointed outthat the apparent anatomical position changes in the radiotheraty of headand neck cancer,the radiation treatment planning may lead to change inthe target and normal tissue and organ doses.During treatment of patientswith CT/MRI images to re-plan design,will be an effective means to sovethe target and normal tissues and organs caused by changes in dosechange.So as to improve the target dose,reducing the dose of normaltissues and organs,improve the quality of long-term survival in patientswith the purpose.Objective: Connect with the number of dynamic design thecharacteristics of Nasopharyngeal carcinoma tumor characteristics to theconcentric retreat,the use of dynamic target with high-risk organmetrology advantage, trying to establish the chance of cure.Methods and Materials: Retrospective collection and analysis of60 hospitalized patients with nasopharyngeal carcinoma in January2006toJanuary2009accepted the radical process intensity-modulatedradiotherapy， including (UICC2002) stage16.6%(10),stage П16.6%(10),stage III25%（15），stage IV A41.6%（25），with a median age46（16-68yrs). The outline of the target volume of the nasopharynx andneck is the nasopharyngeal gross tumor volume (GTVnx), positive lymphnodes (GTVlnL and GTVlnR), clinical target volume1(CTV1), clinicaltarget volume2(CTV2) and cervical lymph nodes to prevent theDistrict(CTVln). Prescription dose, respectively,is PGTVnx69~75Gy，PGTVln(R/L)66~70Gy，PCTV164~68Gy，PCTV255~60Gy，PCTVln50~55Gy. The multiple Replanning IMRT was delivered in33-35fractions. Replanning were carried out at the15th,25thand30thfractionof full Treatment course with a new simulation computed tomography(CT) and magnetic resonance imaging (MRI) scanning for all patients,and audit by the physician with a superior. SPSS13.0software package.Compare the dose of target and normal tissue and organ in one-wayplanning with multiple replanning. Late toxicities were scored based onthe RTOG criterion. The Kaplan-Meier method was used to calculate thelocal-regional control rate (LRC), and far turn the survival rate (D-MFS)and cumulative survival (OS).Results: The statistical analysis showed that, depending on the extent ofinvolvement, T1~2in patients with tumor gross target volume dose (the PGTV-b) in multiple replanning was significantly higher than in one-wayplanning(the PGTV-a)（72.17±0.79Gy VS70.96±1.13Gy，p=0.007）.brainstem dose (D1cc) in Multiple replaning slower than in one-wayplanning（41.13±3.744Gy VS42.54±3.83Gy，p=0.004）. Spinal cord,optic nerve, left and right temporal lobe, left and right parotid, left andright mandibular joint were not significantly different. T3~4in patientswith tumor gross target volume dose (the PGTV-b) in multiple replanningwas significantly higher than in one-way planning(the PGTV-a)（73.65±1.94Gy VS72.82±1.95Gy，p=0.000）. Brainstem dose (Dmax,D1cc) inMultiple replanning slower than in one-way planning（49.02±7.23Gy VS54.14±8.81Gy，P=0.033；39.38±5.66Gy VS43.63±7.09Gy，P=0.026）.Optic nerve dose (D01) in Multiple replanning slower than in one-wayplanning(46.47±9.81Gy VS55.23±9.99Gy，p=0.000). Left parotid dose(D50) in Multiple replanning slower than in one-way planning(29.44±3.49Gy VS31.04±3.76Gy,p=0.000). Right parotid dose (D50) inMultiple replanning slower than in one-way planning(21.92±4.14GyVS29.80±3.52Gy，p=0.000). The left and right mandibular joint was nosignificant difference. The median follow-up interval was34months. The3-year local control, distant metastasis-free survival,Disease specialSurvival and overall survival rate was100%,83.3%,88%and91.7%.Late toxicities were mainly grade I-II，Some patients had grade Ⅲ.Conclusion: Multiple replanning for NPC patients during IMRT helps to ensure adequate doses to the target volumes and acceptable doses toOARs, with higher LC and OS and less toxicities.