Introduction – Opportunistic salpingectomy (OS) is a procedure that involves the removal of the fallopian tubes at the time of other surgeries for the prevention of ovarian cancers. Ovarian cancer consists of distinct histotypes including: High Grade Serous Carcinoma (HGSC), Clear Cell Ovarian Carcinoma (CCOC), endometrioid carcinoma, mucinous carcinoma and Low Grade Serous Carcinoma (LGSC). The origin of the most lethal histotype, HGSC, is the fallopian tube. OS aims to prevent ovarian cancer by removing the origin of these cancers. We hypothesize that post-OS, a histotype distribution shift will show a reduction in the overall numbers of ovarian cancers, including HGSC. We aim to show that tumors arising post-OS are molecularly distinct from tumors arising in patients with fallopian tubes in-tact.

Methods: We will use a case-based and population-based approached to identify tumors that arise following OS. Cox-proportional hazard analysis will be used to determine the histotype distribution shift following OS. We will qualitatively analyze tumors using low-pass whole genome sequencing, targeted sequencing and immunohistochemistry. We aim to acquire 150 carcinomas and 300 controls to perform targeted sequencing on 275 cancer genes (6M reads).

Results - We collaborated with institutions from across Canada, the U.S.A, the Netherlands and the United Kingdom. Our preliminary cohort consists of 19 cases with  26.3% HGSC cases (n=5), 26.3% are endometrioid carcinoma (n=5), 21.1% (n=4) are CCOC, 10.5% are LGSC (n=2), and three cases are mucinous carcinoma (15.8%). One case had a precursor lesion and the tumor had a TP53 frameshift mutation (c229fs) with null p53 staining.

Conclusion – Our preliminary data indicates a histotype distribution shift following opportunistic salpingectomy. HGSCs are reduced relative to historical numbers of ovarian cancers from patients with fallopian tubes in-tact. We welcome others to join this collaborative effort.