Correlation between prolactin and breast density.

A20

Among women, breast cancer is the most common cancer and is second only to lung cancer in the number of deaths per year. In 2006, approximately 212,920 new cases will be diagnosed in the United States and 41,430 women will die from breast cancer. Thus, breast cancer represents a major burden to women and methods to impact risk identification and modification are paramount. Aside from age the most consistently reported breast cancer risk factor is mammographic (breast) density. Comparing the highest category of breast density to the lowest, there is a 4- to 6-fold increased risk of breast cancer development. The variation that is observed in breast density is likely due to hormones and/or growth factors. One of those hormones for which there is substantial laboratory and in vitro data suggesting a role in breast carcinogenesis is prolactin. Prolactin acts as a mitogen and differentiating agent, especially during pregnancy and lactaction by acting directly on mammary epithelium to produce lobuloalveolar development. Using a cross-sectional study design, we examined the correlation between breast density and serum prolactin levels in postmenopausal women (n=515) enrolled in MAMS (Mammograms and Masses Study). All women selected for this study had no history of cancer and had a recent (within 3 months) mammogram. In addition women were selected from both the well control group (n=372; women with negative mammograms) and from the benign control group (n=143; women with benign breast masses). Four women were excluded from the analysis due to outlying prolactin values as determined by the generalized extreme studentized deviate many-outlier detection method. Due to the non-normal distribution of prolactin, Spearman's correlation coefficient were used to examine the correlation between prolactin and breast density. In the overall sample (all postmenopausal women), a weak but positively significant correlation was observed between prolactin and breast density (r=0.120, p-value=0.006). Because prolactin levels may be influenced by hormone use (HRT), we stratified the sample based on current HRT use. No significant correlations were observed for postmenopausal women on HRT. However, for postmenopausal women not on HRT (n=384), the positively significant correlation between prolactin and breast density persisted (r=0.148, p-value=0.004). When the analysis was further stratified by control group, the correlation decreased slightly for those women classified as well (r=0.115, p-value=0.04), but increased slightly for those women classified as benign (r=0.246, p-value=0.037). Our data suggest that prolactin is positively correlated with breast density and may play a role in breast cancer carcinogenesis, especially for women with benign breast masses. This correlation will need to be further explored, but if it's collaborated by other studies, then prolactin antagonists may be explored as potential chemopreventive agents for breast cancer.