Efficacity of Deep Inspiration Breath Hold and Intensity-modulated Radiotherapy in Preventing PErfusion Defect for Left Sided Breast Cancer (EDIPE)

Breast irradiation is known to cause radiation-induced heart disease (RIHD) many years later after radiotherapy. Recent studies suggest that RIHD could be an earlier complication and that subclinical cardiac injury can be detected such as myocardial perfusion defects. Myocardial perfusion single photon emission computed tomography (SPECT) is a sensitive and specific technique able to detect perfusion abnormalities which are more frequent in left-sided breast cancer patients because of the cardiac exposure. The most used technique for breast cancer irradiation is tangential opposed field, but this technique exposes the left anterior descending coronary artery to high dose during left breast irradiation. There are different cardiac sparing techniques to reduce heart exposure such as: * Deep inspiration breath-hold (DIBH) which displaces the heart out of the radiation beam * Intensity-modulated radiation therapy (IMRT) which decreases heart exposure to high doses but changes the dose distribution in the heart and increases lower doses.