18F-FLT PET performs better than 18F-FDG PET in differentiating malignant uterine corpus tumors from benign leiomyoma

摘要

Purpose: The aim of this study is to test the hypothesis that positron emission tomography (PET) with 3′-deoxy-3′-[ 18F]- fluorothymidine ( 18F-FLT) can differentiate malignancy from benign leiomyoma better than PET with 2-deoxy-2-[ 18F]fluoro-D-glucose ( 18F-FDG), and to evaluate whether 18F-FLT and 18F-FDG uptake correlate with immunohistochemical index of cell proliferation. Methods: The protocol of this prospective study was approved by the institutional ethics committee, and all patients gave written informed consent. Fifteen patients (aged 26-65 years, median 44 years) with uterine corpus tumor which has the possibility of being leiomyosarcoma underwent 18F-FLT and 18F-FDG PET scans. Maximum standard uptake value (SUV max) of PET scans and Ki-67 labeling index of surgical specimens were evaluated. Mann-Whitney's U test was used for comparing uptakes between benign and malignant, and linear regression analysis was used for evaluating the correlation between Ki-67 labeling index and SUV max. Results: Five cases were diagnosed as malignant (leiomyosarcoma for 3 cases, and carcinoma for 2 cases), and the others were benign leiomyoma. Sensitivity and negative predictive value of both tracers for detecting malignancy was 100 %. Specificity, positive predictive value and accuracy of 18F-FLT PET were higher than those of 18F-FDG PET. Difference in SUV max between malignant and benign was significant for 18F-FLT PET (P0.01), but not for 18F-FDG PET. While all the malignant cases showed positive uptake in both tracers, a case of leiomyosarcoma with huge necrosis showed relatively low uptake. Uptake of 18F-FLT showed better correlation with Ki-67 labeling index compared with 18F-FDG (R 2 = 0.91 vs. R 2 = 0.26). Conclusion: Negative findings on additional 18F-FDG or 18F-FLT PET may rule out the possibility of malignancy for the patients with suspected leiomyosarcoma diagnosed by conventional methods. 18F-FLT PET is superior to 18F-FDG PET in differentiating malignant from benign leiomyoma. Moreover, 18F-FLT uptake correlated well with the immunohistochemical index of cell proliferation.