Dose evaluation in breast brachytherapy using different ¹²⁵I seeds: A Monte Carlo approach

A very common type of cancer among women is the breast cancer. The treatment choice depends, among several factors, on the clinical stage of the disease and the age. One way to treat breast cancer is the permanent breast seed implant, with Iodine-125 (¹²⁵I). Since they present some advantages: possibility to treat solid tumors, near the tumor site, induction of little trauma and strong lethality to cancer cells. In Brazil, a new ¹²⁵I seed was developed at the Instituto de Pesquisas Energéticas e Nucleares to be applied in brachytherapy. Given the large number of women diagnosed with breast cancer, in this work, the dose determination in organs and tissues was undertaken, considering this new seed and a commercial, Amersham 6711-Oncoseed®, employing the Monte Carlo method. Moreover, for a better understanding of the radiation doses delivered to different patients, the breast volumes were modified. For this purpose, the MCNPX Monte Carlo code was utilized coupled with female virtual anthropomorphic phantoms. The results pointed out the highest dose values for the breast and skin. Furthermore, the dose results for both types of seeds were very similar. (author)