Study Of Intensity Modulated Radiation Therapy Of Cervical Cancer

Purpose:The aim of this article is to analysis the efficacy and complications of Itensitymodulated radiation Therapy(IMRT) of cervical cancer, evaluate the feasibility ofIMRT as a conventional means. The target volume and critical organs of IMRT areanalysised, compared with 3-Dimensional conformal radiation therapy (3DCRT) bythe parameters as such dose volume histogram(DVH).Materials and Methods:Between July 2005 and December 2006, twenty eight women with cervical cancerundergoing IMRT were selected for this study. All of them, fifteen women acceptedIntensity modulated whole pelvic radiotherapy(IM-WPRT),ten women with Intensitymodulated small pelvic radiotherapy(IM-SPRT),three women with Extended fieldIntensity modulated radiotherapy(EF-IMRT,including whole pelvic and paraaorticlymph node). A planning CT scan of each patient was obtained followingadministration of oral and i.v.. The gross target volume is primary disease and the areainvolved.A clinical target volume (CTV) was contoured consisting of the uppervagina, parametria, uterus (if present), and presacral and pelvic lymph noderegions(common, internal and external iliac nodes). Stage Ib1 disease treated withpostoperative radiotherapy without pathologic risk factors(including positive nodes,parametrial extension, and positive or close surgical margin, capillary lymphatic spaceinvolvement) covers primarily the pericervical regions, wthout presacral region. Thepara-aortic lymph node (PALN) intensity modulated radiation therapy (IMRT) wastaken in patients with paraaortic lymph node metastases. The clinical target volumewas expanded by 1 cm to create a planning target volume (PTV) in all directions butA/P dirctions. The samll bowel, rectum, bladder, pelvic bone marrow, femurheads,kidneys and spinal cord were delineated as risk organs for each patients. 5-7-or9-field, 6-MV-xray, coplanar IMRT plans were generated for all patients.Doseconstrain isV40＜40％for rectum, V40＜40％for bladder, V30＜40％for samll bowel,V20＜50％for marrow of pelvis, V40＜5％for femur head,V25＜33％for kidney, D 1cc＜40Gy for spinal cord. All patients received intracavitary branchtherapy after or inIMRT. Concurrent radio-chemotherapy was taken in Twenty two patints. The acutegastrointestinal and genitourinary and hematologic toxicity during treatment wasscored according to RTOG. Conformal plans were created: a four-field box, 15MV-xray,for comparison with IMRT, protecting normal tissue using MLC.Isodose distributionsand dose-volume histogram(DVH) were compared.Both plans were normalized todeliver 45—50.4Gy/1.8Gy/f to PTV.Results:During treatment, IMRT was well tolerated, The acute gastrointestinal andgenitourinary and hematologic toxicity during treatment were Grade 1(50％,46.4％,25％),Grade 2(25％,7.1％,50％), Grade 3 or more (0,3.6％,10.7％). Follow-up4-20months,mean 13.3months,median 14months.All of them, three patient developeddistant metastases(2 chest,1 ovaries), seven percent of the patients suffered Grade 1late gastrointestinal complications, no late genitourinary complications andlymphedema of the leg. The one-year overall survival is 100％.IMRT plans provided excellent PTV coverage, approximate 100％of CTV and5.76％of the PTV on average received the prescription dose. The averagepercentage of the PTV receiving 110％and 115％of the prescription dose was 7.26％and 0.13％, respectively.At high dose level,it is no significant difference that thevolume of the risk organ was radiated compared IM-WPRT with IM-SPRT;at lowdose(＜30Gy),the volume of the risk organ radiated in IM-WPRT was more.Compraed with 3DCRT, two plans both resulted in excellent CTV/PTVcoverage.the dose that 1％of PTV of pelvic IMRT was received was more. at10-30Gy dose level,the radiated risk organs volume in IMRT plan were less, 1％ofsmall bowel and pelvic bone marrow in IMRT plan were lower.At 45Gy doselevel,The radiated volume of samll bowel,rectum,bladder, pelvic bone marrow werereduced by 11％,45-47％,33—42％,8-16％. The para-aortic lymph node (PALN)intensity modulated radiation therapy (IMRT) protected kidney and spinal cord.Conclusion:IMRT of cervical cancer is more excellent than 3DCRT, at dosimetries,complications associated with treatment and curative effect.Duringtreatment,IMRT was well tolerated.But some problems are needed to resolve in thefuture.