ABSTRACTBACKGROUND : Differentiating recurrent brain metastases (BM) from treatment-related changes post-radiotherapy remains challenging. PURSUE (NCT04410367) evaluated various lesion uptake metrics to establish image interpretation criteria to detect recurrent BM with 18F-fluciclovine PET. METHODS : Patients with BM were enrolled if they had a previously irradiated MRI-equivocal ‘reference' lesion and were planned for craniotomy. PET with 18F-fluciclovine (185 MBq) was performed 18F-fluciclovine uptake on static PET images (10-20-minutes post-injection) versus histopathological standard-of-truth was assessed by three blinded readers, as were semi-quantitative (SUV) and dynamic uptake measures, to establish 18F-fluciclovine interpretation criteria. A separate committee reviewed all data to establish interpretation criteria. Following initial review, additional blinded reads were conducted at three timepoints (10-20-, 15-25- and 20-30-minutes) to explore visual-only reads (uptake ≥ parotid/pituitary as reference) and SUV ratio (SUVR)-based criteria (SUVpeak(lesion-to-pituitary)). RESULTS : Twenty-three reference lesions from 23 subjects underwent histopathological analysis; 10 (43%) were confirmed as recurrence. At 10-20-minutes post-injection, the highest performing qualitative measure was ‘uptake higher than parotid' (specificity: 92-100%, sensitivity: 40-80% across readers). SUVmax was a high-performing metric on ROC analysis (AUC: 0.87, sensitivity: 80%, specificity: 85% for SUVmax threshold=4.8). Dynamic measures provided no further diagnostic value. Additional reads showed visual-only interpretation was optimal at 15-25-minutes (sensitivity: 60-90%, specificity: 77-100%). SUVR-based interpretation using a threshold of 1.1 provided 70-80% sensitivity and 85% specificity. CONCLUSION : PURSUE established effective histopathologically verified 18F-fluciclovine interpretation criteria for diagnosing recurrent BM post-radiotherapy that will help evaluate 18F-fluciclovine PET in future studies.
Kotecha et al. (Sun,) studied this question.