A study on contralateral thermoluminescent breast dosimetry of tangential breast irradiation using 6 MV linear accelerator beams

Tangential beam radiotherapy is a treatment used for early stage, breast cancer treatment, when the goal is breast conservation. This method allows skin sparing and avoids irradiation of the lungs and the contralateral breast. In the case of a one sided breast cancer, scatter radiation to the contralateral breast can cause either erythema or desquamation if the allowable skin dose is exceeded, and a secondary malignancy if the glandular tissue absorbs more than the dose limit for breast. While shielding techniques are available elsewhere like Intensity Modulated Radiation Therapy (IMRT) and positioning techniques, these are not much put to use in the Philippines. This study will be the first in the country to measure the scatter dose received by an intact, contralateral breast during tangential beam radiotherapy for an early stage breast cancer. A sample of thirty patients with an intact contralateral breast undergoing tangential beam radiotherapy will be asked to participate. Four thermoluminescent dosimeters (TLDs) will be placed each five centimeters posterior, anterior, left and right lateral to the nipple for each patient under 1.5 cm bolus material. Each patient will have one control TLD for reference. TLDs will be read at the National Cancer Center in South Korea. The effective dose on each patient will be compared to the dose limit for breast in order to classify whether or not the hospital techniques put the patients on a risk for a secondary malignancy. © International Federation for Medical and Biological Engineering 2007