Objective: To evaluate the incidence of early cardiac injury in patients with
left-sided breast cancer receiving hypofractionated
radiotherapy after
breast conserving surgery, and to investigate the correlation between cardiac injury and hypofractionated
radiotherapy dose. Methods: We prospectively enrolled 103
breast cancer patients who received whole breast with or without regional nodal irradiation after
breast conserving surgery using either deep inspiration breath-hold (DIBH) or free breathing (FB)
radiotherapy technique. Cardiac examinations that included N-terminal pro-
B-type natriuretic peptide (
NT-proBNP), electrocardiogram, and myocardial perfusion imaging were performed routinely before and after
radiotherapy. The effects of heart dose, systemic
therapy and individual factors (Framingham score) on the incidence of
cardiac events were analyzed. Results: The median age was 48 years. The mean dose (Dmean) of the heart, left anterior descending coronary artery (LAD), left ventricular (LV), and right ventricular (RV) were 4.0, 16.9, 6.3, and 4.4 Gy, respectively. With a median follow-up of 13.4 months, no patient had clinical cardiac abnormalities. The incidence rates of subclinical
cardiac events at 1- 6- and 12-month were 23.5%, 31.6%, and 41.3%, respectively. The DIBH group had a lower mean dose, maximum dose, and V5-V40 in the heart, LAD, LV, and RV than the FB group (P<0.001). Univariate analysis showed an increased incidence of subclinical
cardiac events with heart Dmean >4 Gy, LAD V40 > 20%, LV Dmean >6 Gy, RV Dmean >7 Gy, or cumulative doses of
anthracycline or
taxane > 300 mg/m(2) (All P<0.05). Anti-HER2 targeted
therapy, endocrine
therapy and Framingham score were not associated with the incidence of subclinical
cardiac events (all P>0.05). Multivariate analysis demonstrated that Dmean of LV and RV were independently associated with the increased incidence of subclinical
cardiac events. Conclusions: Early subclinical
heart injury are found in patients with
left-sided breast cancer after hypofractionated
radiotherapy. The increased incidence of subclinical
cardiac events after
radiotherapy is positively associated with the cardiac radiation doses.