The Use of Intensity Modulated Radiotherapy as a Mean of Reducing Dose to Bone Marrow for Patients with Cancer Cervix Treated at Nci, Cairo, Egypt. Dosimetric Study

Abstract

Purpose : To test the use of Intensity Modulated Radiotherapy (IMRT) to spare the bone marrow (BM) in patients treated with cancer cervix through using the bone marrow an organ at risk. Patients and methods : Thirteen patients with stage (IB2-IIIB) intact cervix cancer were included; C-T simulation was done with contrast and full bladder with slice thickness 2.5 mm. Clinical Target Volume (CTV) included the cervix, uterus, upper half of the vagina, parametrium and regional lymph nodes. The CTV was expanded by 1 cm to form the Planning Target Volume (PTV). The organ at risk (OAR) included the bladder and rectum, the external contour of the pelvic bones to define the Pelvic Bone Marrow (PBM). Four plans were done for every patient with anteroposterior-posteroanterior (AP/PA), three dimensional conformal radiotherapy (3DCRT), IMRT, bone marrow-sparing intensity-modulated pelvic radiotherapy (BMS-IMRT). Results : BMS-IMRT reduced the V20, V30, V40 and V45 of the BM in comparison to 3DCRT and IMRT plans. Reduction in V20 with BMS-IMRT plan compared to 3DCRT ( p < 0.03). The PBM volume receiving 5, 10 and 20 Gy was lower AP/PA than BMS-IMRT ( p < 0.01, p < 0.001 and p < 0.04 respectively). The volumes of the rectum and bladder receiving dose of 40 and 45 Gy were lower in BMS-IMRT plan compared to AP/PA and 3DCRT plans with p = 0.01 for both of them. PTV cover was better in the BMS-IMRT and IMRT plans. Conclusion: BMS-IMRT decreased the irradiated BM volume compared to other techniques. Thus using BMS-IMRT is recommended to decrease hematological toxicity and avoid treatment interruption.