Intensity Modulated Whole Pelvic Radiotherapy (IM-WPRT) Reduces Rectum, Bladder And Bone Marrow Doses In Patients With Cervical Cancer After Hysterectomy: A Dosimetric Analysis

Purpose: To compare restrospectively the conventional radiotherapy and Intensity modulated radiotherapy(IMRT) techniques delivered to the whole pelvis in reducing the volume of normal tissues with cervical cancer after hysterectomy.Methods and Materials: 15 patients with cervical cancer after hysterectomy were selected .A clinical tumor volume ( CTV ) was countoured on each planning computed tomography scans of patients .CTV included parametria, presacral space,upper vagina,pelvic and common iliac lymph nodes.The Pinnacle and Corvus planning system were used to develop conventional and IMRT plans,respectively. Conventional treatment planning included AP/PA field(2f) and four-field( 4f) using 18-MV photos.Five-field( 5f-IMRT ) ,seven-field (7f-IMRT)and nine-field (9f-IMRT)techniques using 6-MV photos were used for IMRT.All treatment plans were prescribed to deliver 45Gy to the planning tumor volume(PTV). All plans were normalized so that <97%of PTV received <95%of prescribed dose. The dose volume histograms were used for comparing each planning. Kruskal-Wallis H test was used to compare the volumes of organs at risk (OAR)recieiving doses in excess of 30Gy with different plans.Results: According to dose distribution and spareing of OAR,a similar advantage was noted for the rectum,bladder and bone marrow among IMRT techniques.7f-IMRT planining received more uniform dose coverage than that of 5,9-IMRT, respectively. The mean volume of rectum receiving < 45Gy was significantly lower with 7f-IMRT than with 2f and 4f (p=0.008).Compared with 2f and 4f plans,the mean volume of bladder was reduced with 7f-IMRT at recieving <40Gy,<45Gy(P<0.05).The mean volume of bone marrow was significantly lower with 7f-IMRT at recieving<35Gy compared with 2f and 4f.Conclution: Intensity-modulated whole pelvic radiotherapy can reduce the treatment volume of rectum,bladder and bone marrow for cervical cancer after hysterectomy. It may appears offer several advantages over conventional radiotherapy planning for reducing acute and potentially late treatment-related toxicity.