Epidemiological studies have demonstrated associations between circulating levels of
sex steroid hormones and risk of
breast cancer in postmenopausal women. However, data on associations with
breast cancer survival are limited. We measured levels of
estradiol,
estrone,
testosterone, and
sex hormone-binding globulin (SHBG), in serum collected on average 30 months after diagnosis from 358 postmenopausal women diagnosed with stage I-IIIA
breast cancer between 1995 and 1998 who participated in a multiethnic, prospective cohort study. Women were followed through December, 2012. We evaluated associations between log-transformed analytes and
breast cancer-specific and all-cause mortality fitting multivariable Cox proportional hazards models. Over a median of 14.5 years of follow-up, 102 deaths occurred; 43 of these were due to
breast cancer. In models adjusted for ethnicity/study site, age, body mass index, and
tumor stage, increased levels of log-transformed SHBG were associated with reduced risk of both
breast cancer-specific mortality (hazard ratio, HR 0.48; 95 % confidence interval, CI 0.26-0.89) and all-cause mortality (HR 0.64, 95 % CI 0.43-0.97). There were no associations between levels of
estradiol,
estrone, or
testosterone for either endpoint. In subgroup analyses, after correction for multiple testing, increased
estrone was significantly associated with reduced risk for
breast cancer-specific mortality among participants with ER-negative
tumors (HR 0.16, 95 % CI 0.05-0.63) but not among participants with ER-positive
tumors. Increased serum levels of SHBG were associated with decreased risk of
breast cancer-specific and all-cause mortality in women with
breast cancer. These results should be confirmed in larger
breast cancer survivor cohorts.