CT Simulation to Evaluate of Pelvic Lymph Node Coverage in Conventional Radiotherapy Fields Based on Bone and Vessels Landmarks in Prostate Cancer Patients

Background: Radiotherapy is the gold standard for treatment of prostrate cancer as it can cover an adequate area of tissues at risk for metastasis. Objectives: We evaluated the Pelvic lymph node coverage of conventional radiotherapy fields based on bone and vessels landmarks using computed tomography (CT) simulation in patients with prostate cancer referred to Shohada-e-Tajrish hospital. Patients and Methods: In this cross sectional study, 40 patients with prostate cancer at the Stage T1c to T3b were studied. Pelvic lymph nodes were contoured by using pelvic vessels as surrogate markers. The distances were measured at different points of anterior-posterior (AP) and lateral fields and distances > 5 mm or more between the contoured nodes and the field borders. Results: Mean and standard deviation of the aortic bifurcation from the superior border was 4.73 +/- 1.16 cm, the distance of common iliac bifurcation from the superior border was 1.11 +/- 1.25 cm, the mean (SD) distance of right external iliac from the lateral border of AP field was 2.06 +/- 0.48 cm and for left external iliac artery was 1.90 +/- 0.56 cm. The distance of the external iliac artery from the anterior border of the lateral field was 2.30 +/- 0.74 cm. The distance of the external iliac artery from pelvic rim was 0.59 +/- 0.59 cm, distance of bifurcation of iliac from sacroiliac joint was 0.82 +/- 1.01 cm, the size of the pelvic rim was 12.30 +/- 0.64 cm, sacral width was 8.29 +/- 1.01 cm, anterior promontory symphysis distance was 12.02 +/- 0.92 cm and posterior promontory symphysis distance was 10.98 +/- 0.73 cm. Conclusions: We observed that conventional radiotherapy using CT simulation based on bone and vessels landmarks provided adequate coverage of pelvic lymph nodes in our patients with prostate cancer.