4′-[Methyl- 11C]-thiothymidine PET/CT for proliferation imaging in non-small cell lung cancer

Abstract

A new tracer, 4′-[methyl- 11C]-thiothymidine ( 11C-4DST), has been developed as an in vivo cell proliferation marker based on the DNA incorporation method. This study evaluated the potential of 11C-4DST PET/CT for imaging proliferation in non-small cell lung cancer (NSCLC), compared with 18F-FDG PET/CT. Methods: Eighteen patients with lung lesions were examined by PET/CT using 11C-4DST and 18F-FDG. We constructed decay-corrected time-activity curves of 9 major regions as the mean standardized uptake value. We then compared the maximum standardized uptake value (SUVmax) of lung tumors on both 11C-4DST and 18F-FDG PET/CT with the Ki-67 index of cellular proliferation and with CD31-positive vessels as a marker of angiogenesis in surgical pathology. Results: NSCLC was pathologically confirmed in 19 lesions of 18 patients. Physiologic accumulation of 11C-4DST was high in liver, kidney, and bone marrow and low in aorta, brain, lung, and myocardium. Biodistribution of 11C-4DST was almost stable by 20 min after injection of 11C-4DST. Mean 11C-4DST SUVmax for lung cancer was 2.9 ± 1.0 (range, 1.5-4.7), significantly different from mean 18F-FDG SUVmax, which was 6.2 ± 4.5 (range, 0.9-17.3; P < 0.001). The correlation coefficient between SUVmax and Ki-67 index was higher with 11C-4DST (r = 0.82) than with 18F-FDG (r = 0.71). The correlation coefficient between SUVmax and CD31 was low with both 11C-4DST (r = 0.21) and 18F-FDG (r = 0.21), showing no significant difference between the tracers. Conclusion: A higher correlation with proliferation of lung tumors was seen for 11C-4DST than for 18F-FDG. 11C-4DST PET/CT may allow noninvasive imaging of DNA synthesis in NSCLC. Copyright © 2012 by the Society of Nuclear Medicine, Inc.