Postoperative breast radiotherapy (RT) has been associated with increased risk of heart toxicity. However, there is a lack of knowledge for radiation-induced early cardiovascular injury, especially for hypofractionated RT. This study aims to prospectively detect and predict early clinical or subclinical cardiac events in women undergoing adjuvant RT for breast cancer.

Women with left-sided breast cancer undergo hypofractionated RT at either free-breathing or deep inspiration breath-hold. The incidence and potential clinical, dosimetric and biological indicators of early clinical or subclinical cardiac injury are investigate at 2 years.

Inclusion Criteria:

• Primary left-sided breast cancer post surgery
• Planning for adjuvant breast/chest wall +-RNI

Exclusion Criteria:

• History of cardiovascular disease
• Previous chest radiation
• Bilateral breast cancers

women with left-sided breast cancer planning for adjuvant radiotherapy