Detection of colorectal cancer using 18F-FLT PET: Comparison with 18F-FDG PET

Objectives The purpose of this study was to investigate the feasibility of 3'-deoxy-3'-¹⁸F-fluorothymidine(FLT) positron emission tomography (PET) for the detection of colorectal cancer, in comparison with 2-deoxy-2-¹⁸F-fluoro-D-glucose (FDG) PET, and investigate correlation of the two radiotracers used with proliferative activity as indicated by Ki-67 index.

Methods A total of 26 patients with newly diagnosed colorectal cancer were examined with FLT PET and FDG PET. Tumor lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semi-quantitative analysis, the maximal standardized uptake value (SUV)was calculated.

Results In all 26 patients, colorectal cancers were detected by both FLT PET and FDG PET. The mean (±S.D.) values of FLT SUV in colon cancer (5.4±2.4) and in rectal cancer (5.6±1.3) were significantly lower than the corresponding values of FDG SUV (12.4±6.3 and 12.5±4.7, respectively) (p<0.003). There was no significant correlation between Ki-67 index and either FLT SUV or FDG SUV.

Conclusions In this comparative study, although uptake of FLT was found to be significantly lower than that of FDG, both FLT PET and FDG PET were able to detect colorectal cancers in all 26 patients. Neither of the two radiotracers used reflected proliferative activity.