Radiotherapy Reduces Risk of Breast Cancer Mortality, Increases Risks of Other Cancers

Radiotherapy is responsible for a significant reduction in breast cancer mortality; however, the treatment may lead to the development of a different cancer or heart disease in the future.

A new study, published in the Journal of Clinical Oncology, estimates the risks of radiotherapy for breast cancer through a systematic literature review that includes lung and heart doses in regimens for breast cancer during 2010 to 2015.

The authors conducted a meta-analysis of data from previous randomized trials that compare radiotherapy versus no radiotherapy. The analysis included data on 40,781 women who had participated in 75 clinical trials, and rate ratios for secondary cancer, lung cancer, and cardiac mortality were collected. Patient information, like tumor characteristics, treatments, and cancer recurrence, were considered in the trials.

Following the meta-analysis, the researchers were able to calculate the risks for other cancers among certain population categories with radiotherapy utilization. The risk for lung cancer is approximately 4% for long-term and continuing smokers, and 0.3% for nonsmokers. For cardiac mortality, the absolute risk is estimated at approximately 1% for smokers and 0.3% for nonsmokers.

The study did not discover any information on the association between radiotherapy and heart disease development, and therefore could not draw a conclusion. The researchers also note their limitations in the study, as they did not know all the causes of death or smoking habits among the trial participants. However, the research still demonstrates the influence of radiotherapy on smokers and their risks of future diseases.

“For long-term smokers irradiated today, the estimated combined risks from radiotherapy are a few percentage points if smoking continues, which may outweigh the reduction in breast cancer mortality; however, smoking cessation substantially reduces risk,” concludes the study. “For healthy nonsmokers, the estimated absolute risks of lung cancer or cardiac mortality from radiotherapy add up to < 1%, which, for most women, is much smaller than the benefit from radiotherapy.”

Reference

Taylor C, Correa C, Duane FK, et al. Estimating the risks of breast cancer radiotherapy: evidence from modern radiation doses to the lungs and heart and from previous randomized trials. J Clin Oncol. 2017;35(15):1641-1649. doi: 10.1200/JCO.2016.72.0722.