Postmenopausal levels of oestrogen, androgen, and SHBG and breast cancer: long-term results of a prospective study

Nine prospective studies have now reported on the association between endogenous sex hormone levels in postmenopausal women and subsequent breast cancer risk (Moore et al, 1986; Wysowski et al, 1987; Barrett-Connor et al, 1990; Gordon et al, 1990; Garland et al, 1992; Helzlsouer et al, 1994; Toniolo et al, 1995; Berrino et al, 1996; Dorgan et al, 1996; Thomas et al, 1997; Zeleniuch-Jacquotte et al, 1997; Hankinson et al, 1998; Cauley et al, 1999; Kabuto et al, 2000). The Endogenous Hormones and Breast Cancer Collaborative Group (TEHBCCG) conducted a pooled analysis of the original data of these studies and concluded that both oestrogen and androgen hormones were strongly associated with risk (TEHBCCG, 2002). Remaining questions include how long prior to diagnosis the associations between hormone levels and breast cancer are observed and whether androgens play a part independent of their role as substrates for oestrogen production. The New York University (NYU) Women's Health Study was one of the first prospective studies to report a positive association between oestrogens and androgens and breast cancer risk (Toniolo et al, 1995). We expand here our initial results that were based on 130 cases for oestrogen analyses and 85 cases for androgen analyses. The present report includes 297 cases diagnosed between 6 months and 12.7 years after enrollment in the study. This study has nearly twice as many cases as any previously published cohort study. Owing to the large sample size and extended follow-up, we were able to assess the association of breast cancer risk with hormone levels in serum samples collected five or more years prior to diagnosis. To explore whether the presence of a growing cancer results in an increase in circulating hormone levels, we also examined the rate of change per year in hormone and sex-hormone binding globulin (SHBG) levels in 95 cases and their matched controls who contributed a second blood donation within 5 years of diagnosis.