HealthDay News — According to a study published in the Journal of Clinical Oncology, the absolute risks associated with modern radiotherapy are higher for smokers than nonsmokers for patients with breast cancer.

Carolyn Taylor, DPhil, from the University of Oxford in the United Kingdom, and colleagues estimated the absolute long-term risks of modern breast cancer radiotherapy. 

They conducted a systematic literature review of lung and heart doses in breast cancer regimens published from 2010 to 2015. 

Individual patient data for 40,781 women randomized to breast cancer radiotherapy versus no radiotherapy were meta-analyzed to yield rate ratios (RRs) for second primary cancers and cause-specific mortality and excess rate ratios (ERRs) for incident lung cancer and cardiac mortality per Gy.

The researchers found that the average radiation doses were 5.7 and 4.4 Gy for whole lung and whole heart, respectively. Lung cancer incidence ≥10 years after radiotherapy had a RR of 2.10 on the basis of 134 cancers (0.11 ERR per Gy whole-lung dose).

On the basis of 1253 cardiac deaths, the RR was 1.30 for cardiac mortality (0.04 ERR per Gy whole-heart dose). The estimated absolute risks from modern radiotherapy were about 4 and 0.3% for long-term continuing smokers and nonsmokers, respectively, for lung cancer, and 1 and 0.3% for smokers and nonsmokers, respectively, for cardiac mortality.

“Smoking can determine the net effect of radiotherapy on mortality, but smoking cessation substantially reduces radiotherapy risk,” the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.

References

Taylor C, et al. “Estimating The Risks Of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses To The Lungs And Heart And From Previous Randomized Trials”. Journal of Clinical Oncology. 2017. doi: 10.1200/JCO.2016.72.0722 [Epub ahead of print]

Shaitelman SF, Howell RM and Smith BD. “Effects Of Smoking On Late Toxicity From Breast Radiation”. Journal of Clinical Oncology. 2017. doi: 10.1200/JCO.2017.72.2660 [Epub ahead of print]

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