Role of an EpCAM auto-antibody in ovarian cancer patients with special regard to disseminated tumor cells in bone marrow

Abstract

e16557 Background: EpCAM is a tumor associated antigen which is frequently expressed in ovarian cancer. Recently, an autoantibody (AAB) against EpCAM has been identified in ovarian cancer patients. Autoantibodies are immunogene factors and might be of prognostic importance. We showed that disseminated tumor cells (DTC) in bone marrow carry the EpCAM antigen on their surface and correlate with poorer progression free survival (PFS). Here, we evaluated whether EpCAM-AABs have an impact on clinical parameters or the presence of DTC in ovarian cancer patients. Methods: EpCAM-AABs were determined in sera of 28 healthy voluntary age matched females and 62 patients with primary epithelial ovarian cancer before and after platinum-based chemotherapy using a recombinant EpCAM-epitope for antibody- detection by ELISA technique. Mean follow up time was 13 months. DTC in BM were detected by immunocytochemistry applying the pan cytokeratin antibody A45-B/B3. All samples exceeding the mean antibody titer of healthy controls plus 2 standard deviations were considered positive. Results: The antibody titer of healthy controls was 0.061 + 0.015. Using a cut-off value of 0.091, we found 9/62 (15%) ovarian cancer patients to be positive for EpCAM-AABs after first-line treatment. Interestingly, no positive AAB-titers were seen before therapy. Using the paired T-Test, we noted a significant posttherapeutic increase of AABs (CI 0.95, p < 0.0001). Analysis of PFS, FIGO stage, resection status, grading, age, sensitivity to platinum based chemotherapy and DTC did not reveal significant associations with positive EpCAM-AAB titers. Conclusions: The clinical course of ovarian cancer patients and the prevalence of DTC were not altered by EpCAM-AABs. Interestingly, we observed an increase of antibody-levels after first-line treatment. For further validation, we intend to extend our patient collective. In future, it might also be interesting to investigate the impact of AABs on response to targeted therapies against EpCAM. No significant financial relationships to disclose.