Aerobic Fitness Is Related to Myocardial Fibrosis Post-Anthracycline Therapy.

Adjuvant anthracycline chemotherapy for breast cancer is associated with cardiotoxicity and reduced cardiorespiratory fitness (VO2peak). PURPOSE We evaluated the impact of anthracyclines on left ventricular (LV) function and tissue characteristics using cardiovascular magnetic resonance imaging (CMR) to determine their relationship with VO2peak. METHODS Women with breast cancer who had not yet received treatment (No-AT, n=16) and had received anthracycline treatment ~one year earlier (Post-AT, n=16), and controls without cancer (CON, n=16) performed a maximal exercise test and a comprehensive 3T CMR examination including native myocardial T1 mapping, where elevated T1 times are indicative of myocardial fibrosis. ANOVA and linear regression were used to compare CMR variables between groups and to determine associations with VO2peak. Sub-group analysis was performed by categorizing participants as 'fit' or 'unfit' based on whether their VO2peak value was greater or less than 100% of reference value for age and body size, respectively. RESULTS LV end-diastolic volume, ejection fraction, and mass were similar between groups. Post-AT, T1 times were elevated (1534±32 vs 1503±28ms, p<0.01) and VO2peak (23.1±7.5 vs 29.5±7.7mL/kg/min, p=0.02) was reduced compared to CON. In No-AT, T1 times and VO2peak were similar to CON. In the Post-AT group, T1 time was associated with VO2peak (R=64%), whereas in the absence of anthracyclines (i.e., No-AT and CON groups), T1 time was not associated with VO2peak. Regardless of group, all fit women had similar T1 times; while unfit women Post-AT had higher T1 than unfit CON (1546±22 vs 1500±33ms, p<0.01). CONCLUSIONS Following anthracycline chemotherapy, an elevated T1 time suggesting greater extent of myocardial fibrosis was associated with lower VO2peak. However, those who were fit did not have evidence of myocardial fibrosis following anthracycline treatment.