LAUSR

75% of ovarian cancer (OC) cases are detected at an advanced stage. State–of–the–art diagnostic tools don9t show sufficient sensitivity, especially in diagnosing early–stage disease. Still, due to lack in alternatives, these methods are used for monitoring BRCA mutation carriers, who face a high penetrance of OC. A 41–year old BRCA1 mutation carrier decided to undergo risk–reducing bilateral salpingo–oophorectomy (rrBSO), currently the only effective way of reducing the OC risk. The day before surgery, 20ml of peripheral blood were drawn to test for the presence of circulating tumor cells (CTCs) by applying a microfluidic device (Parsortix system) and subsequent qPCR. Furthermore, a lavage of the uterine cavity was performed as previously described. According to state–of–the–art techniques, no signs of cancer were present. However, microscopic malignant lesions at both ovaries and the right diaphragm were observed, and final histopathology revealed FIGO IIIB serous OC. Multiple precursor lesions (STICs) were observed in the fallopian tube. qPCR of preoperative enriched cell fraction indicated the presence of CTCs. Analysis of the lavage sample using TP53 mutation analysis revealed 17% mutant allelic fraction. The same mutation was identified in different STIC and invasive lesions. This case shows that early detection of high–grade serous OC does not necessarily translate into a stage shift, but easier to resect disease. Considering the lag–time between STIC to clinically–overt OC development, both described methods present an opportunity for monitoring high–risk patients to delay rrBSO. Both methods proved to be able to diagnose occult OC, and even carry the potential of detecting STICs. Citation Format: Elisabeth Maritschnegg, Eva Obermayr, Barbara Holzer, Noreen Gleeson, Florian Heitz, Leon Massuger, Gunda Pristauz Telsnigg, Adam Rosenthal, Fabian Trillsch, Els Van Nieuwenhuysen, Michael Zikan, Paul Speiser, Robert Zeillinger. DETECTION OF A CLINICALLY OCCULT OVARIAN CARCINOMA BY NEW DIAGNOSTIC TOOLS – A CASE REPORT [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr DPOC-009.