Oral contraceptive use and other risk factors in relation to HER-2eu overexpression in breast cancer among young women.

摘要

This study was undertaken to explore whether the incidence of breast tumors that overexpress HER-2eu protein product (HER-2eu+) is more strongly associated with oral contraceptives (OCs) and other factors than is the incidence of tumors that do not (HER-2eu-). In a population-based sample of women <45 years, 42.9% (159 of 371) of in situ and invasive breast cancer cases were HER-2eu+ as assessed by immunohistochemistry in archived tissue. Polytomous logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for HER-2eu+ and HER-2eu-breast cancer, as compared with 462 population-based controls, in relation to OCs and other factors. The ratio of the ORs (HER-2eu+ versus HER-2eu-tumors) was used as an indicator of heterogeneity in risk. There was little heterogeneity in risk for OC use of 6 months or more by HER-2eu status (age-adjusted ratio of ORs, 1.29; 95% CI, 0.83-2.00). Among early pill users (< or =18 years of age) heterogeneity was apparent (2.39; 95% CI, 1.08-5.30), which was attenuated in a multivariate model (1.99; 95% CI, 0.87-4.54); among cases with estrogen receptor-negative tumors, heterogeneity increased to 5-fold. For other risk factors, there was no marked heterogeneity between + and - tumors for HER-2eu. In summary, the incidence of breast cancer among younger women in relation to OC use at an early age varied with HER-2eu status, with the odds ratio for +tumors twice that for -tumors.