18FDG-PET/CT versus Contrast Enhanced CT in detection of mucinous ovarian cancer recurrence: comparative study Omnia Talaat1, Mai Amr1, Ismail Ali2, Badr Abdel Maksoud3, Shaimaa Farouk3, Ibrahim Nasr3 1Nuclear Medicine Unit, Radiation Oncology Department, National Cancer Institute, Cairo University. 2Radiology Department, Faculty of Medicine, Zagazig University. 3Clinical Oncology and Nuclear Medicine Department, Faculty of Medicine, Zagazig University Journal: Egyptian J. of Nuclear Medicine Accepted for publication: April 2024 Abstract Introduction: Mucinous ovarian carcinoma (MOC) is a unique and uncommon kind of ovarian cancer (OC). The diagnosis of tumor recurrence may be difficult to achieve with traditional imaging methods based on anatomical variations, such as the discovery of a new aberrant lesion or changes in the size of an existing lesion. A solution to these issues has been suggested: fluorine-18-fluorodeoxyglucose (18F-FDG) with Positron Emission Tomography (PET). Our aim was to assess the added value of 18F-FDG PET/CT in the detection of MOC recurrence and its effect on patient management compared to contrast enhanced computerized tomography (CECT). Material and methods: All patients underwent 18F-FDG PET/CT and CECT for detection of MOC recurrence. PET/CT and CT were interpreted separately and the significance of difference between them was evaluated. Results: The study included 59 patients, 18 and 29 out of them were proven to have local and distant recurrence respectively. PET/CT demonstrated lower false negative rate compared to CECT (1.7% vs. 11.9%) and greater sensitivity (SN) , positive predictive value (PPV), negative predictive value (NPV) and accuracy, but the same specificity (SP) in recurrence detection (97.9%, 90.2%, 87.5%, 89.8%, and 58.3%, vs. 85.1%, 88.9%, 50%, 79.7%, and 58.3%, respectively) and showed significantly higher sensitivity for detection of omento-peritoneal and LNs metastases (mets) (36 and 27 versus 22 and 18, p- 0.0001 and 0.004, respectively). Both modalities were comparable in identifying distant organ mets (p >0.05). PET/CT changed patient management in 25.4% of patients, from no therapy to local and systemic therapy in one and seven patients respectively, and from local to systemic therapy in another seven patients (p= 0.001). Conclusion: 18F-FDG PET/CT showed higher SN and accuracy than CECT in MOC recurrence detection, mainly the omento-peritoneal and nodal deposits, which allowed better guidance for proper therapy planning