The Comparison of Radiation Dosimetry of Rectal Cancer in Two Supine and Prone Positions

Colorectal cancer is the most common gastrointestinal cancer and the fourth leading cause of death in the world. This study aimed to investigate and compare dosimetric differences in radiation therapy for rectal cancer in two supine and prone positions.

In a cross-sectional study in Milad Hospital in Isfahan, the CT scan data of 30 patients who are candidates for radiation therapy for rectal cancer were sent to the treatment design software. The target organ PTV (Planning Target Volume) and the organs at risk including the bowel bag and the bladder were contoured by the radio-oncologist. The design of three-dimensional conformal radiotherapy (3D_CRT) was designed using 3 and 4 field methods and 18 megavolt energy. Finally, using the dose-volume distribution curve dose-volume histogram (DVH), the dosimetry of the target organs and the organs at risk were discovered and converted by assimilation.

The average dose that will receive by the bowel bag and bladder in the prone position in the 3-field method was significantly lower than the other studied methods. In addition, the position of the 3-fields supine delivers a higher dose to the organs at risk than the 3-fields prone. However, organs of the four fields in supine position will receive a higher dose compared to the other fields.

In radiation therapy of rectal cancer, due to the improvement of the coverage of the target volume and better dose design, it is suggested than the treatment with the 3-field in position prone.