1331 Occult lesions in ovarian cancer risk-reducing surgery

Introduction/Background Risk-reducing bilateral salpingo-oophorectomy (rrBSO) is the most effective strategy for reducing ovarian cancer incidence and cancer-related mortality in women at increased genetic risk. For BRCA1 and BRCA2 mutation carriers, this surgery can reduce the risk of ovarian cancer by approximately 80%. The incidence of occult ovarian malignancy at the time of risk-reducing surgery (RRS) has been reported to range from 2 to 17%, predominantly located in the fallopian tube. Methodology We performed a retrospective observational study of women with hereditary mutations for breast and ovarian cancer who underwent RRS for ovarian cancer at an oncological referral centre, from January 2018 to June 2023. The aim of this study was to determine the rate of occult ovarian malignancy in this at-risk population. Results We included 109 patients who underwent RRS for ovarian cancer, with a mean age at the time of the surgery of 51.5 years (SD 10.9 years). A high-risk pathogenic variant was detected in 93.6% and a moderate-high risk in 6.4% of the women. 52.3% of the women had a personal history of breast cancer. 91.7% of the women underwent RRS by minimally invasive surgery. Only 3 patients (2.7%) had post-operative complications. Anatomopathological analysis revealed occult tumour cells in 4 cases (3.7%): serous tubal intraepithelial carcinoma was detected in 2 patients (1.8%) and tubal high-grade serous carcinoma in 2 patients (1.8%). Occult ovarian carcinoma was found only in women with high-risk pathogenic variant. Preoperatively, all these patients had normal pelvic imaging results and CA-125 levels. Patients with tubal high-grade serous carcinoma completed surgical staging and final FIGO 2018 stages IC3 and IIB were established. Conclusion Risk-reducing surgery demonstrate to be safe, with a minimal surgical complication rate. Anatomopathological analysis reported occult ovarian lesions in 3.7% of women, consistent with the current literature, all of them with high-risk pathogenic variant. Disclosures Nothing to disclose.