Abstract
Epidermal growth factor receptor (EGFR)-targeted cancer therapy requires an accurate estimation of EGFR expression in tumors to identify responsive patients, monitor therapeutic effect, and estimate prognosis. The EGFR molecular imaging is an optimal method for evaluating EGFR expression in vivo accurately and noninvasively. In this review, we discuss the recent advances in EGFR-targeted molecular imaging in cancer, with a special focus on the development of imaging agents, including epidermal growth factor (EGF) ligand, monoclonal antibodies, antibody fragments, Affibody, and small molecules. Each substrate or probe, whether it is an endogenous ligand, antibody, peptide, or small molecule labeled with fluorochrome or radionuclide, has unique advantages and limitations. Antibody-based probes have high affinity but a long metabolic cycle and therefore offer poor imaging quality. Affibody molecules promise to surpass antibody-based probes due to their small size, stable chemical properties, and high affinity to the target. Small-molecule probes are safe, have favorable pharmacokinetics, and show high affinity and specificity, in addition to having an ideal size, but are inadequate for delayed imaging after injection due to their fast clearance.
Highlights
Clinical Relevance of the EGFR Signaling PathwayThe epidermal growth factor receptor (EGFR) is 1 of 4 members of the human EGFR family of receptor tyrosine kinases.[1]
Radioimmunotherapy with [177Lu]Lu-cetuximab showed significant inhibition of tumor growth (P < .01) and marked reduction in [18F]Ffluorodeoxyglucose (FDG) standard uptake value (SUV), when compared to the control on day 14 after treatment (0.66 + 0.12 vs 0.94 + 0.12, P < .05). These results suggest that radiopharmaceutical [64Cu]Cu-PCTA-cetuximab/[177Lu]Lu-PCTAcetuximab may be useful as a diagnostic tool for patient selection and as a potent radioimmunotherapy agent in EGFR-positive esophageal squamous cell carcinoma (ESCC) tumors
Zhang et al[105] explored the feasibility of using [99mTc]Tc3PRGD2 ([[99mTc]Tc(HYNIC-3P-RGD2)(tricine)(TPPTS)]: where HYNIC is 6-hydrazi nonicotinyl; 3P-RGD2 is PEG4-E[PEG4-c(RGDfK)]2; PEG4 is 15-amino-4,7,10,13tetrao-xapentadecanoic acid; and TPPTS is trisodium triphenylphosphine-3,30,300-trisulfonate) single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging to monitor the efficacy of EGFR-tyrosine kinase inhibitors (TKIs) therapy in patients with advanced-stage lung adenocarcinoma
Summary
The epidermal growth factor receptor (EGFR) is 1 of 4 members of the human EGFR (hEGFR) family of receptor tyrosine kinases.[1]. The multicenter study (Iressa Survival Evaluation in Lung Cancer) revealed that unselected patients receiving gefitinib had no clinical benefits compared to the placebo group in NSCLC.[15,16] These studies have raised awareness for the need to evaluate EGFR expression before targeted treatment in order to select responsive patients and predict clinical results more accurately. Methods to detect expression levels of EGFR protein include biopsy and serological detection. It has become necessary to develop an accurate noninvasive method for detecting EGFR expression in vivo, to select patients potentially responsive to EGFR-targeted treatment, to monitor changes in EGFR expression levels during treatment, and to guide the selection of adequate clinical treatments. EGFR-targeted imaging in vivo could be a valuable tool for noninvasive identification of EGFR expression
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