What Is Theranostics?
Theranostics is a medical approach that combines diagnostics and therapy using the same molecular target. The idea is simple: a diagnostic scan first confirms that cancer cells carry a specific marker. If they do, a treatment that targets that same marker is used to deliver radiation directly to those cells.
This is not a new concept. Radioactive iodine therapy for thyroid cancer, which has been used since the 1940s, is one of the earliest examples of theranostics. Thyroid cells absorb iodine, so radioactive iodine can be used to both image and treat thyroid cancer. Modern theranostics applies this same principle to other cancers using newer molecular targets and radioisotopes.
How Theranostics Works in Practice
The process involves two steps:
Step 1: Diagnostic scan. A PET CT scan is performed using a tracer that binds to a specific protein on cancer cells. If the scan shows strong tracer uptake at the disease sites, it confirms that the cancer expresses the target.
Step 2: Targeted therapy. A therapeutic version of the same molecule, now carrying a treatment dose of a radioactive isotope (typically Lutetium-177), is administered. Because it targets the same protein, it seeks out the cancer cells and delivers radiation directly to them.
This two-step process means patients are selected for treatment based on evidence that their specific cancer carries the target. It is a form of personalised medicine, where treatment is matched to the biology of each patient’s disease.
Current Applications
Prostate cancer: PSMA PET CT scan followed by Lu-177 PSMA therapy. The PSMA protein on prostate cancer cells serves as the target for both imaging and treatment.
Neuroendocrine tumours: Ga-68 DOTANOC PET CT scan followed by Lu-177 DOTATATE therapy. Somatostatin receptors on NET cells are the target.
Thyroid cancer: Diagnostic iodine scan followed by radioactive iodine therapy. The thyroid cell’s natural iodine uptake is the target.
Emerging targets: FAPI (fibroblast activation protein) is being explored as a theranostic target for multiple cancer types. CAIX is being investigated for kidney cancer. Research continues to identify new targets that could expand theranostics to additional cancers.
Visit our radioligand theranostics page to learn more about the treatments available.
Why Theranostics Matters for Patients
The theranostic approach offers several advantages from a patient’s perspective. First, it provides a built-in selection process. Only patients whose cancers express the target are offered the therapy, which increases the likelihood that the treatment will reach the cancer cells. Second, the targeted nature of the treatment means radiation is concentrated at disease sites with relatively less exposure to surrounding healthy tissue compared to conventional external radiation. Third, post-therapy imaging can confirm that the treatment molecule reached the intended targets, providing a verification step.
Theranostics is not suitable for every cancer or every patient. The cancer must express the specific molecular target, and the patient must meet other medical criteria for safe treatment. These decisions are made by the treating team based on a thorough evaluation.
A Growing Field
Theranostics is an active area of medical research. New molecular targets are being discovered, new radioisotopes are being tested, and clinical trials are expanding the range of cancers that can be approached this way. For patients with cancers that express the right targets, theranostics represents a treatment approach that is inherently personalised and continuously evolving.