Radiation-related heart disease: current knowledge and future prospects.

The heart has traditionally been considered a radio-resistant organ that would be unaffected by cardiac doses below about 30 Gray. During the last few years, however, evidence that radiation-related heart disease can occur following lower doses has emerged from several sources. These include studies of breast cancer patients, who received mean cardiac doses of 3–17 Gray when given radiotherapy following surgery, and studies of survivors of the atomic bombings of Japan who received doses of up to 4 Gray. At doses above 30 Gray, radiation-related heart disease may occur within a year or two of exposure and risk increases with higher radiotherapy dose, younger age at irradiation, and the presence of conventional risk factors. At lower doses the typical latent period is much longer and is often more than a decade. However, the nature and magnitude of the risk following lower doses is not well characterized, and it is not yet clear whether there is a threshold dose below which there is no risk. The evidence regarding radiation-related heart disease comes from several different disciplines. The present review brings together information from pathology, radiobiology, cardiology, radiation oncology and epidemiology. It summarises current knowledge, identifies gaps in that knowledge, and outlines some potential strategies for filling them. Further knowledge about the nature and magnitude of radiation-related heart disease would have immediate application in radiation oncology. It would also provide a basis for radiation protection policies for use in diagnostic radiology and occupational exposure.