F-FACBC and F-FDG PET/MRI in the evaluation of 3 patients with primary central nervous system lymphoma: a pilot study.

BACKGROUND

This PET/MRI study compared contrast-enhanced MRI, F-FACBC-, and F-FDG-PET in the detection of primary central nervous system lymphomas (PCNSL) in patients before and after high-dose methotrexate chemotherapy. Three immunocompetent PCNSL patients with diffuse large B-cell lymphoma received dynamic F-FACBC- and F-FDG-PET/MRI at baseline and response assessment. Lesion detection was defined by clinical evaluation of contrast enhanced T1 MRI (ce-MRI) and visual PET tracer uptake. SUVs and tumor-to-background ratios (TBRs) (for F-FACBC and F-FDG) and time-activity curves (for F-FACBC) were assessed.

RESULTS

At baseline, seven ce-MRI detected lesions were also detected with F-FACBC with high SUVs and TBRs (SUV:mean, 4.73, TBR: mean, 9.32, SUV: mean, 3.21, TBR:mean: 6.30). High TBR values of F-FACBC detected lesions were attributed to low SUV. Baseline F-FDG detected six lesions with high SUVs (SUV: mean, 13.88). In response scans, two lesions were detected with ce-MRI, while only one was detected with F-FACBC. The lesion not detected with F-FACBC was a small atypical MRI detected lesion, which may indicate no residual disease, as this patient was still in complete remission 12 months after initial diagnosis. No lesions were detected with F-FDG in the response scans.

CONCLUSIONS

F-FACBC provided high tumor contrast, outperforming F-FDG in lesion detection at both baseline and in response assessment. F-FACBC may be a useful supplement to ce-MRI in PCNSL detection and response assessment, but further studies are required to validate these findings. Trial registration ClinicalTrials.gov. Registered 15th of June 2017 (Identifier: NCT03188354, https://clinicaltrials.gov/study/NCT03188354 ).