2-[11C]thymidine positron emission tomography reproducibility in humans

Purpose: To evaluate the reproducibility of 2-[11C]thymidine positron emission tomography (PET) scanning in patients with advanced intra-abdominal malignancies. Patients and Methods: The reproducibility of 2-[11C] thymidine PET was studied by comparing interpatient and intrapatient variability (coefficient of variability, COV) of both blood and tissue data. Arterial plasma metabolite levels were measured using on-line sampling and high-pressure liquid chromatography. 2-[11C]Thymidine retention in tissue was measured as the standardized uptake value at the end of the scan (SUVend), the area under the time-activity curve (AUC 0-1 hour), and the fractional retention of thymidine (FRT). A group of seven patients were scanned 1 week apart with no intervening anticancer therapy. Results: There was interpatient variability in the levels of 2-[ 11C] thymidine and its main metabolite, 11CO2, in plasma. Variability in 2-[11C]thymidine PET data was greater between (COV: SUVend = 38%, AUC0-1 hour = 32%, FRT = 47%) than within (COV: SUVend = 8%, AUC0-1 hour = 2%, FRT = 9%) patients. There was a borderline significant difference between the paired tumor data for SUVend (P = 0.041), but not for AUC0-1 hour (P = 0.81) or FRT (P = 0.90). There was a good correlation between paired data for SUVend (r = 0.98), AUC0-1 hour (r = 0.99), and FRT (r = 0.95). Conclusions: This is the first report showing that 2-[11C] thymidine PET scanning is reproducible in humans. Repeat scanning of tumor proliferation using 2-[11C] thymidine PET is feasible to perform in human intra-abdominal malignancies and should aid the future rapid assessment of anti-proliferative tumor agents. © 2005 American Association for Cancer Research.