Assessment of the onset of radiation-induced cardiac damage after radiotherapy of breast cancer patients

ObjectivesThe study aimed to evaluate the dose delivered to the heart during radiotherapy of left-sided and right-sided breast cancer (BC) patients, correlate the dose and laterality of radiotherapy to the possible cardiac damage and evaluate whether Left-ventricular Ejection Fraction (LVEF), Troponin-I (TnI), Creatinine Kinase (CK), Creatine Kinase-MB Relative Index (CK-MBRI) or Lactic Dehydrogenase (LDH) could be used to detect the possible onset of radiotherapy-related cardiotoxicity.Subjects and methods80 females were assigned as; 30 left-sided BC patients, 30 right-sided BC patients and 20 healthy females. Patients were treated by radical mastectomy followed by FAC-based chemotherapy and radiotherapy. CT-based 3D-planning was used to generate cardiac dose-volume histograms to assess mean dose received by the heart.Echocardiography was done to all patients before and 1 year after completing radiotherapy. In serum, TnI and CK-MB concentration and CK and LDH activities were determined before and 1 year after radiotherapy.ResultsIn left-sided patients, mean dose delivered to the heart was significantly higher in left-sided patients with significant association with total radiotherapy dose in left- but not right-sided patients. LVEF before and after radiotherapy were statistically different only in left-sided patients. LVEF one year after radiotherapy dropped 20% or more (ΔLVEF) in 6 patients, all were left-sided.Using cut-off values 0.08 ng/mL for TnI and 1.4 for CK-MBRI; 11 left-sided patients had abnormal TnI and CK-MBRI vs 5 right-sided patients, the 6 patients identified with ΔLVEF ≥ 20 were all among them.Conclusionthe mean dose delivered to the heart is significantly higher in left-sided patients, and it was correlated to the total radiotherapy dose. One year after radiotherapy, ΔLVEF is possibly good marker of cardiotoxicity onset, however, the persistent elevation of both TnI and CK-MBRI could identify both patients with cardiotoxicity and patients that are thought to be in subclinical phase of cardiac damage.