Abstract P5-08-23: Ki-67 expression is not a valuable predictive prognostic factor when progesterone receptor expression is high in estrogen receptor-positive breast cancer

Abstract

Abstract Background Immunohistochemistry markers are recognized as a predictive prognostic factor for women with breast cancer. Ki-67 and progesterone receptor (PgR) expression are reported to be independently associated with breast cancer prognosis. Some studies report high Ki-67 expression as a negative predictive marker. Whereas other studies report tendency of similar survival between high and low Ki67 cancers when PgR expression is high. In this study, we examined the prognostic significance of Ki-67 expression under PgR expression status. Methods The records of 2,366 patients were retrospectively reviewed. The patients underwent surgery for primary breast cancer from July 2009 to December 2012 at a single institution. We studied the prognostic significance of Ki-67 expression under PgR expression. We used 20% and 10% as the cut-off value for PgR and Ki-67, respectively. The end point was recurrence-free survival (RFS) evaluated by use of Kaplan-Meier analysis. Result Of the 2,366 analyzed patients, the median follow-up time was 43 months. During follow-up, 44 patients had recurrence, loco-regional recurrence developed in 23 patients and distant recurrence developed in 21 patients. In patients with low PgR expression, high Ki-67 expression group showed significantly worse prognosis compared to low Ki-67 expression group (p=0.005). On the other hand, no significant difference was shown between low and high Ki-67 expression group when PgR expression was high (p=0.637). Also multivariate analysis demonstrated that high Ki-67 expression was an independent prognostic factor only when PgR expression was low. (95% confidence interval [CI], 1.35-10.48; p=0.011) Conclusion This is the largest reported study that prognostic significance of Ki-67 expression is defined by PgR expression. Our study presents that high Ki-67 expression is inversely correlated with recurrence risk in early breast cancer patients only under low PgR expression. At high PgR expression, Ki-67 expression has no influence on breast cancer prognosis. Therefore, attention should be paid to correlation between PgR and Ki-67 expression. Citation Format: Han JH, Kang YJ, Han W, Lee H-B, Kim Y, Yoo T-K, Moon H-G, Noh D-Y. Ki-67 expression is not a valuable predictive prognostic factor when progesterone receptor expression is high in estrogen receptor-positive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-23.