Radiation to heart weakens cardiorespiratory fitness in lung, breast cancer survivors
Radiation dose appears to impair cardiorespiratory fitness in lung or breast cancer survivors, reports a new study.
Researchers enrolled 25 cancer survivors (median age, 63 years; 60 percent female) who had been treated with thoracic radiotherapy with incidental significant cardiac involvement. Cardiorespiratory fitness was measured as peak oxygen consumption; doppler echocardiography was also performed to derive the diastolic functional reserve index (DFRI).
The median mean cardiac radiation dose (MCRD) delivered in the overall cohort was 5.4 Gy, though this was significantly higher in those with lung cancer (10.3 vs 3.7 Gy; p<0.001). The total prescribed dose in the overall cohort was 60.0 Gy and was comparable between lung and breast cancer patients (60.2 vs 60.2 Gy, respectively; p=0.98).
The relative peak oxygen consumption in the overall cohort was 16.8 mL·kg-1min-1, while median DFRI was 27.3. Multivariate linear regression modelling found that MCRD was significantly and inversely correlated with peak oxygen consumption (R, –0.445; p=0.02).
Moreover, researchers found that DFRI (β, 0.0813; p<0.01) and levels of N-terminal pro-brain natriuretic peptide (β, –0.414; p=0.04) were likewise significant predictors of peak oxygen consumption.
“[I]mpairment in cardiorespiratory fitness shows a dose-dependent relationship with the radiation dose to the heart, and is primarily related to impaired diastolic reserve,” said researchers. “This study warrants further investigation into radiation-induced exercise intolerance and the efficacy of interventions to improve cardiorespiratory fitness in this population.”