18F-fluorothymidine (FLT) PET-CT for early response assessment in advanced pancreatic cancer.

Abstract

e21093 Background: Advanced pancreatic cancer has a poor prognosis with a median survival of 6-10 months. There is a need for early non-invasive assessment of treatment response. We evaluated FLT PET-CT combined with a kinetic spatial filtering method (FLT-PETKSF) for detecting response to gemcitabine-based chemotherapy in advanced pancreatic cancer. Methods: Dynamic FLT PET-CT data were collected from patients with confirmed locally advanced or metastatic pancreatic cancer before and 2 weeks after the first cycle of chemotherapy. Changes in tumor FLT-PET variables with treatment were determined. Standardized uptake value (SUV) reduction of 18% was taken as cut-off for response. Voxel quantification of each tumor volume was performed on the filtered data. Each voxel-intensity was normalised by injected dose, body weight and decay corrected to obtain the SUV for the voxel. Changes in high intensity voxels (HiVox: SUV ≥ 2) - were computed. Results: Results of the first 5 patients are discussed. There were 4 primary and 9 metastatic tumors. FLT-PETKSF improved tumor-to-background ratio and enabled visualisation of all the primary and metastatic tumors. The mean (± SD) average and maximum SUV at 60 min (SUV60, av & SUV60, max) of the primary lesions was 2.10 (±0.38) & 4.85 (±1.55) and that of the metastatic lesions was 3.74 (±1.49) & 6.90 (±2.05) respectively. The mean (± SD) percentage reduction in the SUV60, av & SUV60, max, HIVox was 26 (±44), 18 (±38) and 23 (±50) respectively. The changes in the voxel occurrences correlated strongly with the changes in both SUV60, av & SUV60, max (Pearson r-0.9, p=0.001) .Overall, there were 2 partial responders and 3 with stable disease. These responses concurred with response evaluation on mid-treatment CT scan. Conclusions: FLT-PET and FLT-PETKSF enables visualisation of the pancreatic tumors and the liver metastases, and could be used to monitor response to therapy.