How radiotherapy for breast cancer influences long-term the risk of lung cancer and heart disease

This study investigated the results of previous trials to determine the effects of breast cancer (BC) radiotherapy (RT) on the long-term risk of developing other health conditions later in life. This study determined that for long-term smokers, the future health risks associated with RT may outweigh the benefits.

RT is known to reduce the risk of BC-related mortality in suitable patients. It can, however, increase the likelihood of secondary cancers (in particular lung cancer) or heart disease developing later in life. Smoking greatly increases the loss of life associated with both of these conditions. For this reason the risk to smokers and non-smokers must be calculated separately.

This study involved 40,781 women across 647 treatment regimens who were randomly assigned to receive or not receive RT.  The assigned treatment, dose of RT received, any recurrence of cancer, and cause of death or last known date of survival was measured for all participants. The average follow-up time was 10 years.

The average doses of RT received were 5.7 Gy for the lungs and 4.4 Gy for the heart. The risks to smokers and non-smokers were calculated separately. In the case of non-smokers, RT increased the likelihood of lung cancer related mortality by 0.3% and heart disease related death by 0.3%. For continued long-term smokers,  there was a 4.4% greater risk of death for lung cancer and 1% for heart disease.

The study concluded that for long-term smokers the risk of future health issues associated with RT may outweigh the benefits. For non-smokers and ex-smokers, the benefits are far greater than the risks. Smoking may be the biggest factor in determining the long-term health risks of RT.

This study relied on patient information from previous trials, because of this the information cannot be fully verified and in some cases complete information was not available.

Discuss which treatment options are best for you with your doctor.