An observational study using {gamma}-H2AX foci to investigate cardiac doses of radiation following adjuvant radiotherapy for breast cancer: Standard external beam radiotherapy to the breast versus intraoperative radiotherapy.

TPS129 Background: External beam radiotherapy is a gold standard adjuvant treatment after breast conserving surgery for localised breast cancer. A recent phase III trial has shown the non-inferiority of intraoperative radiotherapy compared with external beam radiotherapy (Vaidya J et al. Lancet 2010) with a reduction in radiotherapy toxicity in the intraoperative radiotherapy group (0.5% vs 2.1%; p = 0.002). Intraoperative radiotherapy also has advantages in cost saving and patient convenience, particularly for those living some distance from a cancer centre. There are data to suggest an increase in morbidity and mortality from stroke and heart disease in those exposed to radiation and this includes late effects from breast radiotherapy. Intraoperative radiotherapy uses low energy x-rays (50 KV) and is therefore likely to reduce the radiation exposure of the cardiovascular system compared with external beam radiotherapy. We are using γ-H2AX foci formation in peripheral blood lymphocytes as a surrogate mar...