Comparative Study of Dose Volume Parameters in 2-Dimensional Radiography and 3-Dimensional Computed Tomography Based High Dose Rate Intracavitary Brachytherapy in Cervical Cancer: A Prospective Study

Abstract

Background: Present study compares two high-dose-rate intracavitary brachytherapy (ICBT) planning methods using two-dimensional orthogonal radiography and three-dimensional computed tomography (3D-CT) with regard to dose to target volume and organs at risk (OAR) in carcinoma cervix. Methodology: ICBT plans for 22-patients were compared using 2D planning and three-dimensional computed tomography (3D-CT) planning techniques. 2D treatment plans were generated using 2D-orthogonal images and dose was prescribed at Point A while 3D-CT plans were generated using 3D-CT images after contouring target volume and organs at risk. In 2D planning rectal and bladder doses were assessed as per ICRU-38 and in 3D planning, 0.1cc, 0.2cc, 0.5cc and 1cc doses of bladder and rectum were evaluated. Doses to target and organ at risks (rectum and bladder) were compared for each planning method. Results: Mean dose received by D90, D95 and D100 was 8.05±1.59Gy, 7.19±1.43Gy and 4.79±0.93Gy respectively. ICRU bladder and rectal point doses were 5.19±1.36Gy and 5.03±0.36Gy respectively. Mean dose received by bladder D0.1cc, D0.2cc, D1cc, D2cc and D5cc was 2.38±0.80, 2.22±.75, 1.85±0.64, 1.51±0.64 and 1.29±.49 times higher than ICRU bladder reference point dose. Similarly mean dose received by rectum D0.1cc, D0.2cc, D1cc, D2cc and D5cc was 1.49±0.27, 1.43±.25, 1.25±0.23, 1.09±0.21 and 0.93±.21 times higher than ICRU rectal reference point dose. Conclusion: This study demonstrates suboptimal target coverage and underestimation of dose to OAR by 2-dimensional radiography when actual dose estimation was done by 3-dimensional brachytherapy planning for the same brachytherapy session.