RDC for Diagnostic Imaging

Composed of radionuclide and targeting molecule, RDC (Radionuclide Drug Conjugate) is a very effective tool for cancer diagnosis and therapy response detection. Radiolabeled molecules targeted at tumor-specific biomarkers, such as enzymes, receptors, and transporters in cancer cells represent an intensively investigated and promising class of molecular tools for cancer diagnosis and therapy.

Functional in Vivo Imaging Methods of Tumors

Biomedical imaging is an indispensable tool for cancer research in a wide range of applications, such as screening, prediction, staging, biopsy and therapy guidance, therapy response, therapy planning, and prognosis of cancer.

The variety of imaging approaches is classified into two categories according to their utilization. One is used to provide anatomical and physiological information, including Computed tomography (CT) and magnetic resonance imaging (MRI). The other is used to detect the molecular changes in different diseases including cancerous tissues, such as optical imaging, positron emission tomography (PET), and single photon emission computed tomography (SPECT).

PET and SPECT Imaging with RDC in Vivo

Overview of Nuclear Medical Imaging

The safe clinical application of all the novel anti-cancer therapies depends on in vivo using medical imaging techniques—known as in vivo cell tracking, in which SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) is the most widely used radionuclide imaging tool, as a result of high sensitivity and whole-body quantitative imaging capability.

SPECT and PET Utilized in Nuclear Medical Imaging

Even though radionuclide imaging has lower spatial resolution compared to MRI and CT, PTE and SPECT imaging have a myriad of advantages in whole-body scale accessibility and high sensitivity, which means less administered radiotracers and less toxicity.

Fig.1 Schematic representation of SPECT and PET. (Gawne, P. J., et al., 2022, Chemical Reviews.)

SPECT imaging utilizes gamma-emitters conjugated with antibodies, small molecules, and peptides. In the clinical, the most widely used gamma radionuclide is ⁹⁹mTc with a moderately short half-life, which is 6 hours, long enough for convenient synthesis of radiotracers and short enough to allow tracking of cells only for a few hours.

PET involves the imaging of positron (β+) emitting radionuclides. Besides the organic PET radionuclides, such as ¹¹C and ¹⁸F, the most commonly used radiometals in RDC applied in PET imaging are 68Ga with a moderately short half-life, ⁶⁴Cu (t_1/2 = 12.7 h) and ⁸⁹Zr (t_1/2 = 3.3 d) implement for radiolabeling long-circulating antibodies, nanoparticles, and cells.

Diagnostic Imaging for Cancer by RDC

Even though a number of diagnostic methods are now applied in cancer detection and monitoring, such as clinical symptoms, laboratory analysis, antigen test, and pathologic evaluation, RDC is a rapidly evolving imaging tool with additional information about the molecular characteristics of cancer, which can improve the accuracy of cancer diagnosis in clinical. A myriad of RDC is applied in clinical diagnosis at present.

Colon Carcinoma

Prostate Cancer

Breast Cancer

Glioblastoma Multiforme

Neuroendocrine Tumors

Bladder Cancer

Reference

1. Gawne, P. J., Man, F., Blower, P. J., & TM de Rosales, R. (2022). Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging. Chemical Reviews.