The Basics of Theragnostics in Cancer Care – Treat What You See
Surgery, radiotherapy, chemotherapy, molecular targeted therapy, and immunotherapy are the pillars of cancer care. As every patient and every patient’s cancer is unique, equally important to therapeutics is matching the right patient with the right therapy at the right time. This is done with the help of cancer diagnostics. Theragnostics is a cancer treatment strategy linking cancer diagnostics to targeted radioligand therapy. The principle of theragnostics is to deliver targeted radiation to cancer cells, leading to DNA damage, killing the cancer cells, and leaving the healthy cells unharmed. This approach can be used for both diagnosis and cancer treatment.
The theragnostic approach takes advantage of cancer-specific receptors (grey) on the surface of cancer cells to which theragnostic cancer-targeting drug molecules (A) bind to. Healthy cells do not contain these receptors; hence, the drug explicitly targets cancer cells. Different types of cancer cells may have different receptors, and drug molecules are designed to fit precisely to these receptors – like a key to a lock (C). These cancer-targeting molecules can be connected to radioactive isotopes (B). Together, these two components – a radioactive isotope and a cancer-targeting molecule form a radioligand.
Depending on the application of the radioligand (diagnosis or treatment), the radioactive component can be replaced with either a diagnostic or a therapeutic radioactive isotope (D). Diagnostic isotopes emit radiation that is suitable for positron emission tomography (PET) imaging (left), whereas therapeutic isotopes emit strong enough radiation to cause DNA damage and kill cancer cells (right). Two radioligands, based on the same molecular component, where one is coupled to a diagnostic isotope and the other to a therapeutic isotope, are referred to as a “theragnostic pair” (D). If the diagnostic PET scan detects cancer cells in the body, a patient may be eligible for treatment with the corresponding therapeutic radioligand. Thus, the concept of theragnostics makes it possible to “treat what you see”.
Bodei, L., Herrmann, K., Schöder, H., Scott, A. M. & Lewis, J. S. Radiotheranostics in oncology: current challenges and emerging opportunities. Nature Reviews Clinical Oncology 2022 1–17 (2022) doi:10.1038/s41571-022-00652-y.