EP3 Is an Independent Prognostic Marker Only for Unifocal Breast Cancer Cases

The aim of this study was to evaluate the prognostic impact of prostaglandin E2 receptor 3 (EP3) receptor expression might have on the two different breast cancer entities: multifocal/multicentric versus unifocal. As the prognosis determining aspects, we investigated the overall- and disease-free survival by uni-and multivariate analysis. To underline the study’s conclusion, we additionally considered the histopathological grading and the tumor node metastasis (TNM) staging system. A retrospective statistical analysis was performed on survival related events in a series of 289 sporadic breast cancer (BC) patients treated at the Department of Obstetrics and Gynecology at the Ludwig–Maximillian’s University in Munich between 2000 and 2002. The EP3 receptor expression was analyzed by immunohistochemistry and showed to have a significantly positive association with breast cancer prognosis for both entities, although with major differences. Patients with unifocal BC with EP3 receptor expression showed a significant improved overall survival, in contrast to the patient cohort with multifocal/multicentric BC. In this group, EP3 expression revealed its positive impact merely five years after initial diagnosis. Underlining the positive influence of EP3 as a positive prognosticator notably for unifocal breast cancer, only this patient cohort showed favorable outcomes in staging and grading. Especially EP3 expression in unifocal breast cancer was identified as an independent prognostic marker for the overall survival, when adjusted for age, grading, and staging. Altogether, our results strengthen the need to further investigate the behavior of EP3 in breast cancer and understand why markers linked to inflammation show different effects on prognosis and clinicopathological parameters on each focality type.