Smoking and passive smoking in cervical cancer risk: pooled analysis of couples from the IARC multicentric case-control studies.

BACKGROUND: The independent role of tobacco smoking in invasive cervical cancer (ICC) has been established. We evaluated the potential impact of passive smoking (PS). METHODS: A pooled analysis of 1,919 couples enrolled in one of seven case-control studies involving cervical carcinoma in situ (CIS) or ICC was investigated. Information on smoking and sexual behavior was collected from interviews. Specimens were taken from the cervix and penis for human papillomavirus (HPV) DNA testing. Three PS risk models were constructed with all couples, couples with monogamous women, and couples with lifetime nonsmoking monogamous women. For the third model, the analysis considered potential misclassification of smoking status and was restricted to the risk period for which the woman was exposed to both HPV, a necessary cause of ICC, and PS. Multivariable unconditional logistic regression was used to estimate associations between CIS or ICC and PS. RESULTS: An increased risk was found among couples with both ever smoking men and women (OR = 2.26; 95% CI: 1.40-3.64). No statistically increased risk of CIS was found with PS in the models analyzed. Similar significant increased risks of ICC with PS was found among all couples (OR = 1.57; 95% CI: 1.15-2.15) and couples with monogamous women (OR = 1.55; 95% CI: 1.07-2.23) but not among lifetime nonsmoking monogamous women married to ever smoking men. CONCLUSION: PS could not be detected as an independent risk factor of ICC in the absence of active smoking. IMPACT: The combined effects of exposure to active and PS suggest its potential adverse role in cervical carcinogenesis.