Biomarkers associated with breast cancer are associated with obesity

Background: Obesity is linked to the development of postmenopausal breast cancer, and some studies indicate obesity predicts a worse prognosis for premenopausal women who develop the disease. It was our hypothesis that proteins associated with breast cancer would be associated with body mass index (BMI). Methods: We searched our database of women enrolled in breast health translational research trials for information on BMI and markers predictive of breast cancer (basic fibroblast growth factor (bFGF), prostate-specific antigen (PSA), human kallikrein (hK)2, and urinary plasminogen activator (uPA). Information on BMI and one or more nipple aspirate fluid (NAF) or serum biomarkers was available from 382 women. Results: In this data set, NAF and serum levels of PSA (nPSA and sPSA), and NAF levels hK2, bFGF and uPA were each associated with pre- and/or postmenopausal breast cancer. sPSA was inversely associated with BMI in both pre- (r = −.56, p = .001) and postmenopausal women (r = −.62, p = .0035) without breast cancer. This association was lost when controlling for plasma volume. In women without breast cancer, NAF bFGF (p = .07, premenopausal subjects) and NAF hK2 (p = .09, postmenopausal subjects) were borderline associated with BMI. In women with breast cancer, nPSA was inversely (r = −.53, p = .049) associated with BMI in premenopausal women and directly associated with BMI in postmenopausal women (r = .37, p = .017). nPSA trended higher in hormone sensitive cancers, especially those that expressed progesterone receptor (p = .059). Conclusions: sPSA was inversely associated with BMI in all pre- and postmenopausal women and specifically in pre- and postmenopausal women without breast cancer. NAF PSA was associated with BMI in pre- and postmenopausal women with breast cancer. Evaluating the change in PSA with changes in weight may provide clues regarding a subject's breast cancer risk.