Prevalence and clinical significance of unsuspected intracranial findings in patients undergoing oncological whole body 18F fluorodeoxyglucose (FDG) PET CT imaging

Abstract

Background: 18F –fluoro-2-deoxyglucose (18FFDG PET) provides metabolic information of cancer and is integral in the diagnostic workup  of many malignancies. Most oncological FDG PET scans 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 one can debate 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. 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 obtained.

Results: 3523 WB FDG PET were included. The prevalence of clinically  unsuspected intracranial findings detected was 132 cases (3.7%) and of those the clinically significant intracranial finding was identified in  62 cases (1.4%). 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: The study shows an added benefit in inclusion of brain in the field of view as it leads to early detection and crucial  change in management especially for cancers that have a propensity to metastasis to the brain such as in breast and lung cancer.