DYNAMIC IMAGING OF MENINGIOMA WITH 3 '-DEOXY-3 '-[F-18]-FLUOROTHYMIDINE USING POSITRON EMISSION TOMOGRAPHY: A POSSIBLE PREDICTOR OF TUMOR GROWTH

Abstract BACKGROUND Positron emission tomography (PET) with 3’-deoxy-3’-[18F]-fluorothymidine (18F-FLT) provides a non-invasive assessment of in vivo tumor proliferation that could be useful for predicting growth potential in meningiomas. We aimed to study static and dynamic 18F-FLT PET metrics prospectively to assess metabolic activity of meningioma, and their associations to potential tumor growth on subsequent MRI scans. METHODS Between April 2017 and December 2018, 44 patients harboring MRI-suspected (n = 37) and histologically-verified residual meningiomas (n = 7) underwent a 60-minute dynamic 18F-FLT PET prior to imaging surveillance. Maximum and mean standardized uptake values (SUVmax, SUVmean) with/without normalisation to blood radioactivity obtained from a 40-60-minute static PET image and a 60-minute venous blood sampling were calculated. Total volume of distribution (VT) was estimated by kinetic modeling using a two-tissue reversible compartmental model with a fractional blood volume and metabolite-corrected image-derived input function. Tumor growth rate was calculated by volumetric analysis of subsequent MRI scans. RESULTS At the time of this writing, a total of 53 follow-up MRI scans from 33 patients were available for review, with a median follow-up time of 11 months (range, 4–22.5 months). Tumor growth/progression was observed in 12 cases with a monthly median growth rate of 0.10 cm3 (range, 0.03–3.41 cm3). All 18F-FLT metrics were significantly higher in patients with radiological progression compared to patients with stable findings with maximum tumor-to-blood-ratio (TBRmax) as the most promising imaging biomarker (4.9 ± 1.4 vs. 3.4 ± 1.0, P = .003; Mann-Whitney) and the strongest predictor for tumor progression (hazard ratio, 3.125; 95% confidence interval, 1.390–7.028; P = .006; univariate binary logistic regression). Age, gender, previous residual remnant(s) and initial tumor volume (median, 3.1 cm3; range, 0.2–55.3 cm3) had no influence. CONCLUSION 18F-FLT PET imaging could be a valuable tool in designing a patient-tailored surveillance strategy for patients with asymptomatic meningiomas.