Radiotherapy For Breast Cancer: Higher Lung Cancer Risk In Smokers

Breast cancer patients who smoke are at significantly higher risk of developing lung cancer following radiotherapy, according to new research conducted in the UK. The study revealed that those who continue smoking after their radiotherapy treatment are far more likely to suffer from long-term complications, including lung cancer, compared to non-smokers.

The study, led by Professor Carolyn Taylor of the University of Oxford and funded by Cancer Research UK, examined the effects of radiotherapy on breast cancer patients, particularly those who smoke. Published in the journal Clinical Oncology, the research found that smokers are up to six times more likely to develop lung cancer as a result of radiotherapy, compared to non-smokers.

Radiotherapy is a well-established treatment for early-stage breast cancer, with approximately two-thirds of patients in the UK undergoing this therapy. The treatment significantly reduces the chances of breast cancer recurrence and lowers the risk of death from the disease. However, radiotherapy also carries potential side effects, including an elevated risk of secondary cancers, such as lung or esophageal cancer, and heart disease.

The UK records 56,400 new breast cancer diagnoses annually, making it the most common form of cancer in the country. Despite advancements in treatment, it still claims the lives of 11,500 people each year. The study sheds light on an important factor affecting patient outcomes—smoking status during and after treatment.

For non-smoking breast cancer patients, the study found less than a 1% risk of developing lung cancer due to radiotherapy. However, for those who smoke and continue to do so after treatment, the risk jumps to between 2% and 6%, according to the findings.

Professor Taylor explained, “Radiotherapy is highly effective in reducing breast cancer recurrence, but patients must also understand the potential long-term risks. One of these rare side effects is the development of a second cancer, which can occur years after treatment.”

Taylor’s study is the first of its kind conducted in the UK. She noted that radiotherapy unavoidably exposes nearby tissues, such as the lungs, to radiation while targeting the breast, potentially damaging healthy cells in the process. “Radiotherapy damages the DNA in cells, which helps kill cancer cells but can also affect normal cells. This DNA damage, though rare, can lead to cancer many years later,” she added.

Smoking compounds the risks associated with radiotherapy. The radiation exposure combined with the effects of smoking significantly increases the likelihood of lung cancer in breast cancer patients who continue to smoke after treatment. While the vast majority of breast cancer patients in the UK are non-smokers—only 14% of women in the UK smoke—those who do are at a much higher risk.

Deborah Arnott, CEO of Action on Smoking and Health (ASH), emphasized the need for healthcare professionals to educate patients on these risks. “Smokers undergoing radiotherapy must be warned about the dangers of continuing to smoke and should be offered support to quit. Smoking not only makes radiotherapy less effective but also increases the likelihood of cancer recurrence,” she said.

The findings of this study align with recent updates from Cancer Research UK, which has now identified smoking as a direct cause of breast cancer, alongside known factors like genetics and diet. In response to these growing concerns, the Labour Party has pledged in its general election manifesto to expand smoking cessation services, making them available to all hospital patients, including cancer patients.

This landmark study underscores the increased risks faced by breast cancer patients who continue to smoke following radiotherapy. While radiotherapy remains a powerful tool in the fight against breast cancer, its long-term risks, particularly for smokers, cannot be ignored. Medical experts stress the importance of quitting smoking to enhance treatment effectiveness and reduce the chances of developing secondary cancers, including lung cancer.