Abstract 861: Relationships of prolactin serum levels to breast cancer risk and tumor characteristics in a population-based case-control study from Poland

Abstract

Abstract Background: Prolactin is a peptide hormone that is important in growth and development of the human breast. Prolactin also induces migration, proliferation, and survival of cancer cells in vitro and mammary gland tumorigenesis in animal models. Recent studies suggest that elevated serum prolactin levels are related to increased breast cancer risk, but confirmation and extension of these results are needed. Accordingly, we analyzed associations of serum prolactin levels with breast cancer risk using data from a population-based breast cancer case-control study conducted in Poland. Methods: The Polish study included 2,386 consenting cases with pathologically confirmed breast cancer and 2,502 age and residency matched controls living in Warsaw and Lodz, Poland recruited during the years 2000 to 2003. Participation rates were 79% for cases and 69% for controls. This analysis included 773 cases and 776 controls with available serum and twofold representation of tumor in tissue microarrays. 70% of this study population was postmenopausal. Serum prolactin was measured by immunoassay at Quest Diagnostics. The overall CV for the prolactin serum assay was 99%. Detailed medical history and breast cancer risk factor information were obtained by interview. Tumor pathology data were collected via surgical pathology reports and independently reviewed in the U.S. Among controls, we assessed associations of prolactin levels with breast cancer risk factors using analysis of variance; case-control associations between breast cancer risk and prolactin levels (quartiles) were assessed by logistic regression. Results: Among premenopausal controls, nulliparity was inversely associated with prolactin levels (p=0.05), whereas among postmenopausal women, current/recent use of combined hormone replacement therapy (p<0.0001) and lower body mass index (BMI, p<0.0001) were associated with higher prolactin levels. After adjustment for these and other known breast cancer risk factors, as well as for matching factors, elevated prolactin levels were significantly associated with postmenopausal breast cancer risk (OR=1.95; 95% CI 1.37-2.78, p<0.0001), when comparing the highest quartile of prolactin levels to the lowest. Among premenopausal women, risk also was elevated for all levels of prolactin, but risks were not significant and did not increase in a monotonic pattern. Conclusions: Prolactin levels are significantly associated with breast cancer risk factors and risk for postmenopausal breast cancer. Our results confirm and extend prior studies focused on circulating prolactin levels and human breast cancer risk. Analyses examining associations between prolactin and tumor subclassifications based on immunological staining using tumor tissue microarrays are ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 861.