Radiation injury to cardiac arteries and myocardium is reduced by soy isoflavones.

Objective: The negative effects of incidental radiation on the heart and its vessels, particularly in the treatment of locally advanced non-small cell lung cancer, esophageal cancer, left-sided breast cancer, and lymphoma, are known. Late cardiac events induced by radiotherapy including coronary artery disease, ischemia, congestive heart failure, and myocardial infarction can manifest months to years after radiotherapy. We have previously demonstrated that soy isoflavones mitigate inflammatory responses induced in lungs by thoracic irradiation resulting in decreased vascular damage, inflammation, and fibrosis. In the current study, we investigate the use of soy isoflavones to protect cardiac vessels and myocardium from radiation injury.

Methods: Mice received a single dose of 10-Gy thoracic irradiation and daily oral treatment with soy isoflavones. At different time points, hearts were processed for histopathology studies to evaluate the effect of soy isoflavones on radiation-induced damage to cardiac vessels and myocardium.

Results: Radiation damage to arteries and myocardium was detected by 16 weeks after radiation. Soy isoflavones given in conjunction with thoracic irradiation were found to reduce damage to the artery walls and radiation-induced fibrosis in the myocardium.

Conclusion: Our histopathological findings suggest a radioprotective role of soy isoflavones to prevent cardiac injury. This approach could translate to the use of soy isoflavones as a safe complement to thoracic radiotherapy with the goal of improving the overall survival in patients whose cancer has been successfully controlled by the radiotherapy but who otherwise succumb to heart toxicity.