Abstract PR005: TP53 field defects in uterine fluid are associated with ovarian cancer risk
Authors: Risques Rosana , Smith Thomas H. , Norgaard Zachary K. , Katz Roniz , Lo Fang Yin , Schmidt Elizabeth K. , Higgins Jacob E. , Filipits Martin , Labidi-Galy Intidhar , Cibula David , Dostálek Lukáš , Jelenek Gabriel , Plch Magdalena , Bouda Jiří , Mustea Alexander , Condic Mateja , Grill Sabine , Gleeson Noreen , Oppelt Peter , Pristauz-Telsnigg Gunda , Vanderstichele Adriaan , Obrecht Siel , Rosenthal Adam , Speiser Paul , Salk Jesse 
Published: May 2022

Abstract
Background: High grade serous ovarian cancer (HGSC), the most common and aggressive type of ovarian cancer, is nearly always driven by TP53 mutations, which can be detected in uterine lavages using ultra-deep duplex sequencing. While this finding supports the development of a uterine lavage assay for early HGSC detection, age-related TP53 mutations compromise specificity. The goal of this study was to thoroughly characterize the nature of TP53 mutations identified in uterine lavage of women with and without HGSC to better understand TP53 clonal evolution during aging and to determine its association to HGSC. Methods: Uterine lavages were collected preoperatively in 54 “average-risk” women undergoing gynecological surgery for suspicious masses (34 women ultimately had HGSC, 20 were cancer free) and in 98 “high-risk” women undergoing risk-reducing salpingo-oopherectomy (17 were found to have HGSC or serous tubal intraepithelial carcinomas (STICs), 81 were cancer-free). Ultra-deep (&gt;10,000x), ultra-accurate sequencing of TP53 was performed on uterine lavage DNA using duplex sequencing. Tumors and STICs were also duplex sequenced to determine TP53 tumor-driving mutations. The frequency of TP53 mutations and large TP53 mutant clones (those found in &gt;2 duplex reads) was compared between women with and without HGSC. Results: The tumor-specific TP53 mutation was detected in 53% of lavages from average-risk women with HGSC and in 22% of lavages from high-risk women with HGSC/STICs. As in prior studies, TP53 biological background mutations were identified in nearly all women and their frequency was age-related. TP53 background mutations, however, were more abundant in women with prior chemotherapy, regardless of their cancer status or age. In women without prior chemotherapy and without high-risk of HGSC, having HGSC was associated with a significantly higher frequency of large TP53 mutant clones (p=0.007) and large TP53 mutant clones containing pathogenic mutations (p=0.007) or TP53 mutations commonly found in cancer (p=0.001). Interestingly, women at high risk of HGSC also carried high frequency of large and pathogenic TP53 mutant clones in lavage, even in those cases in which cancer or STICs were not identified. Conclusions: Ultra-sensitive duplex sequencing enabled detection of a patient’s HGSC or STIC driver mutations, respectively, in about half and a quarter of uterine lavages. However, of even greater interest, we observed a significant excess of large and pathogenic TP53 mutant clones in lavages of women with HGSC that were not present in the tumor. These results indicate that TP53 somatic evolution is associated with HGSC development and suggest that the measurement of TP53 mutant clones in uterine lavages harbors value as a predictor of ovarian cancer risk.
Citation Format: Rosana Risques, Thomas H. Smith, Zachary K. Norgaard, Roniz Katz, Fang Yin Lo, Elizabeth K. Schmidt, Jacob E. Higgins, Martin Filipits, Intidhar Labidi-Galy, David Cibula, Lukáš Dostálek, Gabriel Jelenek, Magdalena Plch, Jiří Bouda, Alexander Mustea, Mateja Condic, Sabine Grill, Noreen Gleeson, Peter Oppelt, Gunda Pristauz-Telsnigg, Adriaan Vanderstichele, Siel Obrecht, Adam Rosenthal, Paul Speiser, Jesse Salk. TP53 field defects in uterine fluid are associated with ovarian cancer risk [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr PR005.