Correlation of 4′-[methyl-11C]-thiothymidine PET with Ki-67 immunohistochemistry separately in patients with newly diagnosed and recurrent gliomas

Objective 4′-[methyl- 11 C]-thiothymidine (4DST) uptake on PET was correlated with proliferative activity separately in patients with newly diagnosed and recurrent gliomas. Methods A total of 29 patients, 18 with newly diagnosed gliomas and 11 with recurrent gliomas who underwent 4DST PET/computed tomography (CT) were available for a retrospective analysis of prospectively collected data. The maximum standardized uptake value (SUVmax) of tumor (T) and the mean SUV of normal contralateral hemisphere (N) were calculated, and the tumor-to-normal (T/N) ratio was determined. Proliferative tumor volume (PTV) and total lesion proliferation (TLP) were also calculated. Proliferative activity as indicated by the Ki-67 index was estimated in tissue specimens. Immunohistochemical findings were correlated with 4DST PET parameters. Results All gliomas but three newly diagnosed gliomas had 4DST uptake on PET. No significant differences in SUVmax, T/N ratio, PTV, or TLP were observed between the newly diagnosed and recurrent gliomas. In the former, correlations between SUVmax ( r = 0.57, P = 0.02), T/N ratio ( r = 0.51, P = 0.03), PTV ( r = 0.74, P < 0.001), and TLP ( r = 0.76, P < 0.001) and the Ki-67 index were found. In the latter, the results did not seem to suggest any correlations between any of the PET parameters and Ki-67 index. Conclusion Although preliminary, these results suggest that 4DST PET may be useful for the noninvasive evaluation of proliferation in patients with newly diagnosed gliomas. These data in a small recurrent patient population do not support a clear-cut correlation between 4DST uptake and proliferation.