Kinetics of B-type natriuretic peptide plasma levels in patients with left-sided breast cancer treated with radiation therapy: results after one-year follow up.

PURPOSE: To analyse temporal changes of B-type natriuretic peptide (BNP) used as index of heart remodeling in left-sided breast cancer patients after radiotherapy (RT) and its relationship with dosimetric parameters. METHODS AND MATERIALS: BNP and dose-volume parameters for heart and ventricle were collected in 59 patients (median age 58.0 years) during a 1-year follow-up. Biochemical measurements were performed before the RT treatment (T0), at 15 days during RT (T15day), at the end of RT (TendRT), and then at 1, 3, 6, 9, 12 months (T1, T3, T6, T9, and T12). A logistical regression analysis was performed to identify demographic characteristics, dosimetric variables and risk factors associated with increased values of BNP. RESULTS: The ratio between the BNP value at T12 and the BNP value at T0 (BNPT12/BNPT0 ) increased significantly (p < 0.01). A significant association was found between the variation of BNP values after 1 year and the isodose received by 50% of the volume (D50% (Gy)) both to the heart (p = 0.03) and ventricle (p = 0.04) Conclusions: BNP plasma levels could provide additional information about subclinical RT-induced cardiotoxicity earlier than traditional ecocardiographic data.