TY - JOUR T1 - Repeatability of <sup>18</sup>F-FLT PET in a Multicenter Study of Patients with High-Grade Glioma JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 393 LP - 398 DO - 10.2967/jnumed.116.178434 VL - 58 IS - 3 AU - Martin A. Lodge AU - Matthias Holdhoff AU - Jeffrey P. Leal AU - Asim K. Bag AU - L. Burt Nabors AU - Akiva Mintz AU - Glenn J. Lesser AU - David A. Mankoff AU - Arati S. Desai AU - James M. Mountz AU - Frank S. Lieberman AU - Joy D. Fisher AU - Serena Desideri AU - Xiaobu Ye AU - Stuart A. Grossman AU - David Schiff AU - Richard L. Wahl Y1 - 2017/03/01 UR - http://jnm.snmjournals.org/content/58/3/393.abstract N2 - Quantitative 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) PET has potential as a noninvasive tumor biomarker for the objective assessment of response to treatment. To guide interpretation of these quantitative data, we evaluated the repeatability of 18F-FLT PET as part of a multicenter trial involving patients with high-grade glioma. Methods: 18F-FLT PET was performed on 10 patients with recurrent high-grade glioma at 5 different institutions within the Adult Brain Tumor Consortium trial ABTC1101. Data were acquired according to a double baseline protocol in which PET examinations were repeated within 2 d of each other with no intervening treatment. On each of the 2 imaging days, dedicated brain PET was performed at 2 time points, 1 and 3 h after 18F-FLT administration. Tumor SUVs and related parameters were measured at a central laboratory using various volumes of interest: isocontour at 30% of the maximum pixel (SUVmean_30%), gradient-based segmentation (SUVmean_gradient), the maximum pixel (SUVmax), and a 1-mL sphere at the region of highest uptake (SUVpeak). Repeatability coefficients (RCs) were calculated from the relative differences between corresponding SUV measurements obtained on the 2 d. Results: RCs for tumor SUVs were 22.5% (SUVmean_30%), 23.8% (SUVmean_gradient), 23.2% (SUVmax), and 18.5% (SUVpeak) at 1 h after injection. Corresponding data at 3 h were 22.4%, 25.0%, 27.3%, and 23.6%. Normalizing the tumor SUV data with reference to a background region improved repeatability, and the most stable parameter was the tumor-to-background ratio derived using SUVpeak (RC, 16.5%). Conclusion: SUV quantification of 18F-FLT uptake in glioma had an RC in the range of 18%–24% when imaging began 1 h after 18F-FLT administration. The volume-of-interest methodology had a small but not negligible influence on repeatability, with the best performance obtained using SUVpeak. Although changes in 18F-FLT SUV after treatment cannot be directly interpreted as a change in tumor proliferation, we have established ranges beyond which SUV differences are likely due to legitimate biologic effects. ER -