The Advantage In Dosimetry Of Intensity Modulated Radiotherapy For Treatment Of Patients With Cervical Cancer After Hysterectomy

Objective We evaluated target-volume covrage and organ at risk protection achievedwith intensity modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) throughdosimetric comparison in patients with cervical cancer after hysterectomy in order to providebetter treatment for patients.Methods We selected twenty patients with cervical cancer who still need pelvic radiationafter hysterectomy in Shanxi Province Tumour Hospital during November 2009 to November2011. They aged from 38 to 65 and the median age was 46 with the KPS score above 70. A CTscan of each patient in the treatment position was obtained, then transmitted to the planningsystem (Varian Eclipse Version.8.6.0). Eontouring c1inical target volume(CTV) on the CTslices. CTV was then uniformly expanded by 1.0 cm to create the planning target volume (PTV).The Pinnacle planning system version 7.4f was used to develop CRT and IMRT pIans,respectively. 95 of the PTV received the prescription dose 45Gy. We used dose volumehistograms(DVH) and Isodose line were used to evaluate: the homogeneity of dosedistribution in target-volume between IMRT and CRT; conformity indice of target-volume the two plan ; the maximum dose of distribute to the small intestines, bladder,rectum, bone marrow ; the volume of the small intestines, bladder, rectum, bone marrowunder radiation at different dose levers.Results The conformity index of IMRT plans was distinctly superior than CRT, but thehomogeneity of dose distribution in target-volume between IMRT and CRT had no difference.There was no significantly difference on maximum dose of the bladder between CRT and IMRTp 0.05 , while the maximum dose of small intestine , rectum, bone marrow(46.89Gy, 47.72Gy, 46.52 Gy )in IMRT plans was lower than in CRT plans(52.36 Gy 51.69 Gy 48.21 Gy) p0.05 . Comparing with the CRT plans , the IMRT plans significantly spared 41.29%volume ofsmall intestine , 51.89% volume of rectum, 61.19% volume of bladder, and70.53% volume ofbone marrow at 40Gy levers p 0.05 ; at 30Gy levers the volumes of rectum and bladder inIMRT plans were decreaced by 27.30% and 39.97% p 0.05 , although IMRT plans reducedthe volumes of small intestine and bone marrow, there have no statistical signification p 0.05 .There was no statistical signification between CRT and IMRT at 20Gy. On the other hand , thevolume of the bone marrow in IMRT plans was more than CRT at 10Gy, 5Gy levers p 0.05 .IMRT show better protection on small intestine , rectum, bladder, bone marrow at high doselevers. Conclusions The conformity index of IMRT plans was distinctly superior to CRT. IMRTplans distinctly reduced the volumes of the small intestine , rectum, bladder, and bone marrow athigh dose levels. So, patients with cervical cancer after hysterectomy received IMRT maydiminish the Normal Tissue Complication Probability (NTCP).