Association between smokeless tobacco use and breast cancer among Native-American women in North Carolina

Cigarette smoking and smokeless tobacco use have been associated with the development of a variety of cancers. While cigarette smoking may be associated with breast cancer, smokeless tobacco use has never been evaluated as a breast cancer risk factor. This study explores such an association. A complete census was carried out among Eastern Band Cherokee women aged 18 years and older, residing on tribal lands in western North Carolina. Self-reported alcohol, cigarette and smokeless tobacco use, demographic information, and personal history of breast cancer (stratified by age of onset <55 years or ≥55 years) were obtained by questionnaire. 1,070 out of 1,408 (76%) eligible women were interviewed. Current and former smokeless tobacco use was common (6% and 21%, respectively). Five cases of breast cancer were identified in women under the age of 55 years and 3 cases were found in women at ≥55 years. Only the odds ratio (OR) for younger-onset breast cancer among ever-users of smokeless tobacco was significantly elevated (OR = 7.79, 95% Cl = 1.05-66.0). While the ORs for younger onset breast cancer were elevated among ever-smokers or women reporting at least monthly alcohol use, these were not significant (OR = 8.49, 95% Cl = 0.09-200; and OR = 1.72, 95% Cl = 0.19-15.2, respectively). No ORs were significantly elevated for breast cancer among older women. These preliminary data are the first to document an apparent relationship between smokeless tobacco use and breast cancer risk, but should be confirmed in other studies due to the small number of cases. The nearly 8-fold increase in risk suggests that smokeless tobacco is not a safe alternative to cigarette smoking.