Objective: We investigated 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 investigated 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 semiquantitative 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 (± SD) 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.
Conclusion: 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 was correlated with proliferative activity.