Masaaki Kawai, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, and colleagues conducted a case-control study of women, aged 20–44 years, who were diagnosed with invasive breast cancer (ER-positive, 778; ER-negative, progesterone receptor-negative, and human epidermal growth factor-negative [triple-negative], 182) and 938 women without cancer (controls). The researchers sought to assess the association between smoking and risk of breast cancer.
The researchers found that female ever-smokers were 1.3 times more likely to develop breast cancer (95% confidence interval [CI], 1.1–1.7), including increased risk of ER-positive breast cancer (odds ratio [OR], 1.4; 95% CI, 1.1–1.8), but not triple-negative breast cancer (OR, 1.1; 95% CI, 0.7–1.6). Women who were current or recent smokers with a 10 pack-year or greater history of smoking were at increased risk for ER-positive breast cancer (OR, 1.6; 95% CI, 1.1–2.4), but not triple-negative breast cancer (OR, 1.0; 95% CI, 0.5–1.9).
“The results from this study suggest that smoking history, and particularly longer term, recent smoking, is associated with a modest increase in the risk of ER-positive breast cancer, but not with the risk of triple-negative breast cancer,” the authors write.
One of the study authors received a grant from the Banyu Life Science Foundation International.