Abstract 24082: A Combined Basic Science and PopulationScience Approach Demonstrating the Potential for Simvastatin to MitigateCardiovascular Disease after Lower Hemi Body Radiotherapy

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Radiation is a cornerstone of successful cancer treatment, with one-half to two-thirds of all patients receiving radiotherapy. Survivors of cancer treated with radiation are at increased risk for cardiovascular disease (CVD). Understanding how radiation causes CVD will allow development of novel therapies. Irradiation of the lower hemi body, but not the upper hemi body, with 10 Gy in rats increases risk factors for CVD and results in cardiac fibrosis quantitatively similar to total body irradiation, suggesting radiation injury to the heart can be indirect. Simvastatin, an inhibitor of liver cholesterol synthesis administered continuously to rats (10 mg/kg/day) after 10 Gy lower hemi body irradiation mitigated against increased blood cholesterol and cardiac fibrosis. These findings indicate simvastatin limits transmission of a signal from the lower hemi body that decreases risk for and occurrence of CVD independent of any direct exposure of the heart to radiation. Bivariate examination of 3,607 patients following therapeutic lower hemi body irradiation using Chi-square, Wilcoxon rank-sum and t-tests was used to examine risk factors for CVD in patients diagnosed with congestive heart failure, myocardial infarction, atrial fibrillation, and cardiomyopathy before 80 years of age. We found that 47.4% of patients age 70-80 developed CVD compared to 29.7% who received simvastatin (p= < 0.001, n = 293 and 361, respectively). Patients who were male, overweight, smokers, and had a diagnosis of chronic kidney disease and diabetes also had significantly higher risk of CVD. Race and hypertension were not indicative of increased risk for CVD. These clinical findings, taken together with the results from our animal studies, support a new research paradigm where radiation-induced heart disease can be indirect, with abdominal organs exporting factors that cause CVD. Simvastatin can be developed to mitigate and treat CVD after therapeutic radiation.

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