Evaluation of the effectiveness of testicular shielding in rectal cancer radiotherapy

This study aimed to investigate the effect of local shielding on the reduction of the dose received by the male sexual organs in pelvic radiation therapy. For this purpose, a clinical case, and its corresponding simulation with the Monte Carlo Geant4 toolkit were studied. Here, the 15 MV photon mode of a medical LINAC was used to irradiate the pelvic region of three patients with rectal cancer. Using thermoluminescent dosimeter (TLD) 100, the doses received by the testes, seated out of the field, were measured in two situations, i.e., with and without a testicular shield. After benchmarking the simulation setup by comparing the simulated and experimental PDDs (Percentage Depth Dose) and lateral profiles in a water phantom, the simulation corresponding to the clinical case has been done. Afterward, the desired quantities such as absorbed dose, total equivalent dose, and neutron equivalent dose have been calculated. The results indicate that the local placement of a spherical lead shield leads to a decrease in the absorbed dose received by the testes with a coefficient greater than 2. It was also observed that shielding had a minimal contribution to the production of secondary neutrons and was not seen any sensible change in neutron equivalent dose, whereas a decrease in the total equivalent dose by a factor of 2.2 for the testes was observed. These observations imply that the risk of secondary cancers decreased proportion-ately, as well as a reduction in the risk of permanent infertility for young men.