Evaluation and Comparison of Target and At-Risk Organ Dosimetry in Radiation Therapy of Prostate Cancer Patients Using Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT)

The goal of this study was to make a dosimetric comparison between the absorbed dose distribution of the prostate and the organ at risk (OAR) using two different approaches: three-dimensional conformal radiotherapy (3D-CRT) and Intensity-modulated radiotherapy (IMRT), assesed via treatment planning system (TPS) and thermoluminescence dosimetry (TLD).

In this study, 35 patients with prostate cancer undergoing radiation therapy at Milad Hospital in Isfahan were included. Prostate as target and rectum, bladder and femoral head as healthy organ at risk (OAR) were contoured according to Radiation Therapy Oncology Group (RTOG) criteria. Two separate dosimetry programs IMRT and 3D-CRT have been developed for each patient in order to evaluate the dosimetric status of both methods comparatively. These results were then compared with those of the phantom.

The doses to the bladder, rectum, and femoral head were 50.3, 58.6, and 16.4 in IMRT and 59.6, 68.8, and 34.8 in 3D-CRT, respectively. The dose measured by TLD in all organs in the phantom was higher than the dose calculated by TPS software in the phantom.

The IMRT method is a better method than 3D-CRT due to better coverage of the target volume and reduction of the cumulative dose of organs at risk (OAR). The dose measured by TLDs was higher than the dose calculated by the treatment planning system, which may be due to the fact that the treatment planning system does not calculate the share of scattered radiation in the absorbed dose of organs.