Modelo de Braquiterapia com balão de pertecnetato de sódio-99mTc(Na99mTcO4-) para câncer de mama: avaliação da dosimetria e resposta celular

Abstract

Breast cancer is the most common type of cancer that affects more women worldwide. Among various treatment options, radiotherapy which is often used as a treatment for locoregional recurrences control or to decrease tumor size. In patients with breast cancer at an early stage, a booster dose (boost) in the primary tumor area can be applied after conventional radiation therapy. There are several drawbacks to applying this technique. In this work we aimed to perform a dosimetric analysis in a breast model, where it put a balloon filled with sodium pertechnetate - 99mTc ( Na99mTcO4 -) which in future could be used in preference to other possible therapies. The methodology involved the development of dosimetry in water based on radiochomic films and in a computational voxel thorax model. Calibration protocol achieved a mathematical relation between absorbed dose versus optical density (OD) measured at a set ofradiochromic sample films placed at the surface of the balloon plus 1 cm up to 10 cm far, in which theoretical dose values were provided by MCNP modeling, reproducing the waterequivalent physical simulator. A voxel model of a female thorax, developed at the SISCODES/MCNP codes, received a filled balloon inside. Spatial dose distribution was generated, illustrating the dose received in the chest wall, glandular tissue, breast skin and lung. The dosimetric findings contribute to present the Na99mTcO4 - balloon modality which provides a suitable spatial dose distribution in the tumor bed preserving adjacent health tissues.We also studied the radiobiological response radioressistentes mammary adenocarcinoma cells (MDAMB231) by exposure of these cells to Na99mTcO4- balloon. The findings include the presence of apoptotic cells in the balloon around point out a favorable response. In conclusion, the balloon may represent a viable option in the supplementary tratamemto of breast cancer in patients who have appropriate indication. Irradiation with Na99mTcO4 - takes high doses to the tumor bed, the results were obtained from computational and experimental dosimetry, as well as in vitro response was observed in radiosistent breast cancer cells after 24 hours of exposure to the balloon . This therapy is relatively of low cost, can be commercially available and reduces the irradiation time. It is a possibly contribution to the reduction of local recurrence.