Passive Smoking May Increase Risk of Breast, Lung Cancer
Studies show modest risk for breast cancer, larger risk for lung cancer
FRIDAY, Dec. 4 (HealthDay News) -- In nonsmokers, exposure to secondhand smoke is associated with a modestly increased risk of breast cancer and a significantly increased risk of lung cancer, according to two studies published in the December Cancer Epidemiology, Biomarkers & Prevention.
Peggy Reynolds, Ph.D., of the Northern California Cancer Center in Berkeley, and colleagues studied 57,523 women who were lifetime nonsmokers and had no history of breast cancer in 1997, including 1,754 who developed invasive breast cancer during the next 10 years. In postmenopausal women, they found that low, medium and high cumulative exposures to secondhand smoke were associated with an increased risk of breast cancer (hazard ratios, 1.17, 1.19 and 1.26, respectively).
Susan E. Olivo-Marston, Ph.D., of the National Cancer Institute in Bethesda, Md., and colleagues studied 624 lung-cancer cases and 348 controls, and replicated their findings with another study of 172 cases and 289 controls, all never smokers. In both studies, they found that lifetime nonsmokers who were exposed to secondhand smoke in childhood had a significantly increased risk of lung cancer (odds ratios, 2.25 and 1.47, respectively). Both studies also confirmed that lifetime nonsmokers with a functional mannose binding lectin-2 haplotype who were exposed to secondhand smoke in childhood had a significantly increased risk (odds ratios, 2.52 and 2.78, respectively).
"Our data suggest that genetic background in MBL2 with well-known functional consequences in innate immunity is an important modifier of the association between childhood secondhand smoke exposure and lung cancer risk. These findings are bolstered both by the fact they were replicated in two independent case-control studies and warrant additional studies," Olivo-Marston and colleagues conclude.