# Prevalence and clinical significance of unsuspected intracranial findings in patients undergoing oncological whole-body 18F-FDG PET/CT imaging

## TL;DR

Including the brain in PET/CT scans for cancer patients can reveal unexpected brain issues, leading to changes in treatment.

## Contribution

This study quantifies the prevalence and clinical impact of unsuspected brain findings in oncological PET/CT scans.

## Key findings

- 3.7% of scans revealed unsuspected intracranial findings, with 1.4% being clinically significant.
- PET/CT detected brain metastases with 94.7% sensitivity and 66.7% specificity compared to MRI.
- 78% of patients with significant findings had their treatment plans changed.

## Abstract

Routine oncological whole-body 18F-1-fluoro-2-deoxyglucose (FDG) PET/CT in the majority of institutions is performed from the base of the skull to the mid-thigh. However, at our institution, the brain is included. The aim of this study was to identify the prevalence of unsuspected intracranial findings in patients undergoing oncological 18F-FDG PET/CT examinations with inclusion of the brain in the field of view.

A total of 3,523 patients who underwent oncological limited whole-body 18F-FDG PET/CT scans between February 2019 and December 2021 were retrospectively reviewed. The study variables included the patient's age, sex, type of malignancy, disease stage, and clinical presentation and the presence of clinically unsuspected intracranial findings. The intracranial findings were correlated with brain MRI findings in a subset of patients. Clinical significance, defined by a change in disease stage and/or patient management informed by the identification of unsuspected intracranial findings, was assessed.

In total, 132/3,523 (3.7%) oncological whole-body 18F-FDG PET/CT scans had unsuspected intracranial findings, of which clinically significant unsuspected intracranial findings were found in 62 cases (1.4%). The most common intracranial findings were metastasis, followed by subclinical vascular findings. Moreover, 22/62 cases underwent follow-up brain MRI, and the sensitivity and specificity of the 18F-FDG PET/CT scans were 94.7% and 66.7%, respectively. Data on post-PET/CT management were available for 32/132 patients. A change in management was observed in 25/32 (78%) cases.

The inclusion of the brain in the field of view in oncological whole-body 18F-FDG PET/CT may lead to the early detection of unsuspected intracranial metastases and changes in patient management. This is especially true for breast and lung cancers, which have a greater propensity to metastasize to the brain.