# Auxiliary Value of [18F]F-Fluorocholine PET/CT in Evaluating Post-Stereotactic Radiosurgery Recurrence of Lung Cancer Brain Metastases: A Comparative Analysis with Contrast-Enhanced MRI

## TL;DR

This study shows that [18F]F-fluorocholine PET/CT is more accurate than MRI for detecting brain tumor recurrence after radiosurgery in lung cancer patients.

## Contribution

The study introduces [18F]F-FCH PET/CT as a superior and complementary imaging method to MRI for diagnosing brain metastasis recurrence after SRS.

## Key findings

- [18F]F-FCH PET/CT had higher specificity and accuracy than CE-MRI in detecting brain metastasis recurrence.
- Combining PET/CT and MRI improved diagnostic performance compared to using either method alone.
- Total lesion choline uptake (TLC) was linked to shorter intracranial progression-free survival.

## Abstract

Conventional imaging examinations have limitations in diagnosing brain tumor recurrence. [18F]F-fluorocholine ([18F]F-FCH PET/CT) showed lower uptake in normal brain parenchyma and higher tumor-to-brain contrast. There are few data on the use of [18F]F-FCH PET/CT for detecting brain tumor recurrence. This study evaluated the effectiveness of [18F] F-FCH PET/CT versus contrast-enhanced MRI (CE-MRI) in detecting brain metastasis recurrence after stereotactic radiosurgery (SRS) in 31 lung cancer patients. Among 54 lesions analyzed, [18F]F-FCH PET/CT demonstrated higher specificity and accuracy than CE-MRI. For lesions sized 1.0–2.0 cm, PET/CT outperformed MRI significantly. Combining both methods improved diagnostic performance compared to either alone. Additionally, total lesion choline uptake (TLC) was linked to shorter intracranial progression-free survival (iPFS), identifying it as a prognostic marker. [18F]F-FCH PET/CT is a promising imaging modality for detecting the recurrence of brain metastases in lung cancer patients after stereotactic radiosurgery. Combined [18F]F-FCH PET/CT and CE-MRI enhance diagnostic accuracy and patient management in brain metastasis recurrence after SRS.

Background/Objectives: This study aims to evaluate the additional value of [18F]F-fluorocholine ([18F]F-FCH) PET/CT over contrast-enhanced magnetic resonance imaging (CE-MRI) in detecting the recurrence of brain metastases (BMs) after stereotactic radiosurgery (SRS) in patients with lung cancer brain metastases (LCBMs). Methods: Thirty-one patients with suspected recurrence of BM in LCBM after SRS were enrolled in this retrospective study. They underwent both [18F]F-FCH PET/CT and CE-MRI within 2 weeks. The tumor imaging parameters and clinical features were analyzed. The results of histopathology or radiographic follow-up served as the reference standard for the final diagnosis. Results: In these 31 patients, there were 54 lesions, of which 27 lesions were proven to be BM recurrence, while 27 lesions were non-recurrence. [18F]F-FCH PET/CT showed high radiotracer uptake in recurrent lesions of BM and identified 24 positive lesions (88.89% of sensitivity), while CE-MRI indicated 23 positive lesions (85.19% of sensitivity). [18F]F-FCH PET/CT indicated higher specificity (81.48%) and accuracy (85.19%) in detecting recurrence of BM than CE-MRI (40.74% and 62.96%, both p < 0.05), particularly in frontal lobes and cerebella. For lesion sizes, the accuracy of [18F]F-FCH PET/CT in detecting recurrent lesions was higher than that of CE-MRI for lesions over 1.0 cm but below 2.0 cm (p = 0.016). The detective performance of [18F]F-FCH PET/CT combined with CE-MRI was higher than [18F]F-FCH PET/CT or CE-MRI alone (all p < 0.05). Interestingly, TLC (≥4.11) was significantly correlated with poor intracranial PFS (iPFS), meaning it was a significant prognostic factor for iPFS. Conclusions: This study identified that compared with CE-MRI, [18F]F-FCH PET/CT demonstrated higher specificity and accuracy in diagnosing recurrence of BM in LCBM after SRS. Combining [18F]F-FCH PET/CT with CE-MRI has the potential to improve diagnostic performance for recurrence of BM and management of patient treatment. TLC was an independent risk factor for iPFS.