Prevalence, Clinical Manifestations, and Risk Factors for Cardiac Toxicity
Children's Cancer Survivors Study (CCSS) investigators detailed dose-response evaluations for both radiation therapy and anthracycline administration to analyze risks (self-reported) of CHF, myocardial infarction (MI), pericardial disease, and valvular abnormalities (see Figure 2).
Figure 2. Cumulative incidence of cardiac disorders among childhood cancer survivors by average cardiac radiation dose. BMJ 2009; 339:b4606. © 2009 by British Medical Journal Publishing Group.
Compared with siblings, survivors of childhood cancer were significantly more likely to report CHF (hazard ratio [HR] = 5.9; 95% confidence interval [CI], 3.4–9.6), MI (HR = 5.0; 95% CI, 2.3–10.4), pericardial disease (HR = 6.3; 95 % CI, 3.3–11.9), or valvular abnormalities (HR = 4.8; 95 % CI, 3.0–7.6). Cardiac radiation exposure of 15 Gy or more increased the risk of CHF, MI, pericardial disease, and valvular abnormalities by twofold to sixfold compared with nonirradiated survivors. There was no evidence for increased risk following doses less than 5 Gy, and slight elevations in risk were not statistically significant following doses between 5 to 15 Gy. Exposure to 250 mg/m2 or more of anthracyclines also increased the risk of CHF, pericardial disease, and valvular abnormalities by two to five times compared with survivors who had not been exposed to anthracyclines. The cumulative incidence of adverse cardiac outcomes in childhood cancer survivors continued to increase up to 30 years after diagnosis and ranged from about 2% to slightly over 4% overall, but to much higher cumulative percentages for those receiving the highest cardiac radiation doses and the highest cumulative dose of anthracyclines.
A study of 4,122 5-year survivors of childhood cancer diagnosed before 1986 in France and the United Kingdom also provides evidence for an association between radiation dose and risk of cardiovascular disease. After 86,453 person-years of follow-up (average, 27 years), 603 deaths had occurred. The overall standardized mortality ratio was 8.3-fold (95% CI, 7.6–9.0) higher in relation to the general populations in France and the United Kingdom. Thirty-two patients had died of cardiovascular diseases, which is fivefold (95% CI, 3.3–6.7) more than expected. The risk of dying of cardiac diseases (n = 21) was significantly higher in individuals who had received a cumulative dose of anthracyclines greater than 360 mg/m2 (relative risk [RR] = 4.4; 95% CI, 1.3–15.3) and following an average radiation dose exceeding 5 Gy (RR = 12.5 for 5–14.9 Gy and RR = 25.1 for >15 Gy) to the heart. A linear relationship was found between the average dose of radiation to the heart and the risk of cardiac mortality (excess RR at 1 Gy, 60%).