Abstract Purpose: The association between the expression level of lipocalin2 with cancer progression has already been reported in several tumors such as lung, colon, and breast cancer. However, no previous study has examined the relationship between the circulating level of lipocalin2 and its effect on the prognosis of breast cancer. Thus, this study aimed at assessing whether the preoperative serum level of lipocalin2 is related to the risk of recurrence and death in patients who have undergone curative surgical treatment for breast cancer. Design: A total of 370 histologically proven breast cancer patients who had undergone curative resections of the tumor between Mar 2004 and Jan 2007 were included in this study. The median follow-up time of survivors was 4.35 years. The preoperative serum level of lipocalin2 was assayed by using enzyme-linked immunosorbent assay. Disease-free survival was defined as the time from surgery to the date of the first locoregional recurrence, first distant metastasis, or death from any cause. Univariate survival analysis was performed using the Kaplan-Meier method, and log-rank tests were employed for comparison of survival curves. Multivariate analyses were conducted using Cox's proportional hazard regression model adjusted for age, tumor size, lymph node metastasis, hormone receptor status, adjuvant chemotherapy and hormone therapy. Results: The Kaplan-Meier curve showed that patients with upper three-quarters of lipocalin2 concentration combined had lower survival rates than the patients with lowest quarter concentration (P=0.014). In multivariate analysis, lipocalin2 remained an independent prognostic marker for disease-free survival after adjusting for known prognostic factors. The hazard ratio comparing the uppermost quartile to the lowest quartile of lipocalin2 was 2.33 (95% confidence interval, 1.19-4.56; P=0.015). Conclusions: The results revealed that patients with higher level of lipocalin2 showed significantly lower disease-free survival than patients with lower level. Our study suggests that the higher preoperative level of lipocalin2 may be closely linked to poor prognosis in breast cancer. Further validation is required and functional studies are warranted to elucidate the underlying biological mechanisms for the association. Key words: Lipocalin2 (LCN), serum biomarker, breast cancer, prognosis Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2274. doi:10.1158/1538-7445.AM2011-2274