METASTASES-03 PREVALENCE AND CLINICAL SIGNIFICANCE OF UNSUSPECTED INTRACRANIAL FINDINGS IN PATIENTS UNDERGOING ONCOLOGICAL WHOLE BODY(18) F- FLUORODEOXYGLUCOSE (FDG) PET CT IMAGING.

BACKGROUND: Most oncological 18F –fluoro-2-deoxyglucose (18F-FDG PET) are acquired from the base of the skull to the upper thighs, as lesions that take up FDG are usually within this field of view. Routine inclusion of brain within the field of view of all oncological 18FDG PET/CT studies leads to increase of both time of acquisition and radiation dose (albeit marginal) delivered by the CT component of the study, therefore it can be debated if inclusion brain in oncological 18FDG PET-CT has any additional value. OBJECTIVE: To identify the prevalence of clinically unsuspected intracranial findings in patients undergoing routine oncological 18 FDG PET CT examinations in Aga Khan University Hospital (AKUHN)with the inclusion of the brain in the field of view. METHODS: Patients who underwent oncological limited whole-body 18 FDG PET/CT scan between February 2019 to December 2021 were retrospectively reviewed. The patient’s age, sex, type of malignancy, disease stage, presence of clinically unsuspected intracranial finding, and clinical information was reviewed. Clinical impact of the identified intracranial findings was also recorded. RESULTS: A total of 3523 oncological whole body FDG PET were included in the study. Clinically unsuspected intracranial findings were identified in 132 cases (3.7%) out of which 62 (1.7%) were clinically significant. The most common intracranial finding was metastasis. 22 cases underwent a follow up MRI brain and the sensitivity and specificity were 94.7% and 66.7% respectively. Change in management was seen in 25/32(78%) cases. CONCLUSION AND RECOMMENDATION: Inclusion of brain in the field of view of oncological FDG PET CT can lead to early detection of unsuspected intracranial metastasis resulting in management change especially for malignancies that have a propensity to metastasize to the brain such as in breast and lung cancers.