EF5 is a

nitroimidazole 5-Nitroimidazole is an organic compound with the formula O2NC3H2N2H. The nitro group at position 5 on the imidazole ring is the most common positional isomer. The term nitroimidazole also refers to a class of antibiotics that share similar chemi ...

derivative used in oncology research. Due to its similarity in chemical structure to

etanidazole Etanidazole is a nitroimidazole drug that was investigated in clinical trials for its radiosensitizing properties in cancer treatment. Administration of etanidazole results in a decrease of glutathione concentration and inhibits glutathione ''S' ...

, EF5 binds in cells displaying hypoxia. Non-labeled EF5 has been extensively used in immunohistochemical studies for several years and its hypoxia specificity has been comprehensively evaluated The ¹⁸F-

radiolabeled A radioactive tracer, radiotracer, or radioactive label is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tr ...

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. F ...

of EF5 is being studied for its possibility to be used in

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in Metabolism, metabolic processes, and in other physiological activities including bl ...

(PET) to detect low levels of oxygen in

brain tumors A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and secondar ...

and several other malignant tumors. This can help show how a tumor will respond to treatment. Targeting tumor hypoxia in cancer treatment aims to overcome radiotherapy resistance of hypoxic tumors. Thus, a major clinical implication for ¹⁸F-EF5-PET imaging is expected to be guiding of radiotherapy dose modulation. Clinical studies on ¹⁸F-EF5-PET/CT imaging have indicated clinically acceptable biodistribution and dosimetric profile, and in head and neck cancer also favorable imaging characteristics, prognostic value and repeatability. A recent 18F-EF5-PET/MR study showed promising potential in detecting tumor hypoxia in cervical cancer. However, ¹⁸F-EF5-PET/CT is not feasible in imaging of ovarian cancer due to physiological intra-abdominal ¹⁸F-EF5-accumulation. Further studies evaluating the clinical use of ¹⁸F-EF5 PET imaging in head and neck cancer are ongoing.

References

{{reflist Nitroimidazoles