A study on the contralateral breast dosimetry of tangential beam radiotherapy using 6 MV linear accelerator beams

Abstract

Tangential beam radiotherapy is a treatment used for early stage breast cancer 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. This study was 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, and compare these values with previously reported ranges. A sample of seven patients with an intact contralateral breast undergoing tangential beam radiotherapy were asked to participate. Four thermoluminescent dosimeters (TLDs) were placed each five centimeters posterior, anterior, left and right lateral to the nipple for each patient under 1.5 cm bolus material. TLDs were read at the National Cancer Center in South Korea. The effective dose on each patient were 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. The results show that the values measured are significantly smaller than previously reported values and the dose limit set by the ICRP.