Breast cancer: Smoking wipes out radiotherapy benefit

Modern radiotherapy is an invaluable cancer treatment and can target tumours with unprecedented accuracy. However, in women with breast cancer, continuing to smoke seems to negate the benefits of radiotherapy. Smoking also markedly increases the risk of developing lung cancer and death from cardiac causes caused by radiotherapy.

Researchers performed a meta-analysis of 40,781 women randomly assigned to breast cancer radiotherapy versus no radiotherapy in 75 trials. Women who underwent radiotherapy were twice as likely to develop lung cancer (relative risk 2.1) and 30% more likely to die from cardiac causes than controls at least 10 years after treatment ended.

Modern radiotherapy for breast cancer delivers a lower dose to the lung and heart than the older radiotherapy regimens and machines used in some of the studies. Nevertheless, the authors estimated that approximately 4% of long-term continuing smokers would develop lung cancer because of modern radiotherapy compared to 0.3% of non-smokers. Moreover, approximately 1% of long-term continuing smokers would die from cardiac causes because of modern radiotherapy compared to 0.3% of non-smokers.