Imaging of Integrin αvβ3 Expression in Lung Cancers and Brain Tumors Using Single-Photon Emission Computed Tomography with a Novel Radiotracer 99mTc-IDA-D-[c(RGDfK)]2

Integrin αvβ3 is a molecular marker for the estimation of tumor angiogenesis and is an imaging target for radiolabeled Arg-Gly-Asp (RGD) peptides. In this study, the authors investigated the clinical efficacy and safety of a novel radiolabeled RGD peptide, 99mTc-IDA-D-[c(RGDfK)]2, for the imaging of integrin αvβ3 expression, as a measure of tumor angiogenesis in lung cancers and brain tumors. Five patients with lung cancers and seven with brain tumors underwent 99mTc-IDA-D-[c(RGDfK)]2 single-photon emission computed tomography (SPECT) imaging. Tumors were also assessed using 18F-fluorodeoxyglucose positron emission tomography/computed tomography. Uptake of the radiotracer was expressed as the tumor-to-normal uptake ratio (TNR). All the lung cancers and brain tumors were well visualized on 99mTc-IDA-D-[c(RGDfK)]2 SPECT. TNR for 99mTc-IDA-D-[c(RGDfK)]2 was significantly higher than that for 18F-FDG in brain tumors (6.4 ± 4.1 vs. 0.9 ± 0.4). Proliferation index of brain tumors showed a significant positive correlation with TNR for 99mTc-IDA-D-[c(RGDfK)]2 and 18F-FDG. No laboratory and clinical adverse events were reported after 99mTc-IDA-D-[c(RGDfK)]2 injection. Their results suggest that 99mTc-IDA-D-[c(RGDfK)]2 is an efficacious and safe radiotracer for imaging integrin αvβ3 expression with potential application to monitoring the clinical efficacy of antiangiogenic agents in malignant tumors. In addition, this is the first clinical application of radiolabeled RGD peptides for SPECT imaging of brain tumors.