Targeted Radionuclide Therapy — An Emerging Class of Cancer Therapeutic and Imaging Agents

The goal of targeted radionuclide therapy is to enable potent yet controlled delivery of radiation treatment directly to the tumor environment while minimizing radiation exposure to normal tissue. In addition, targeted radionuclides can also be used as imaging agents to select patients for therapeutic applications; this is known as “theranostics.”

Radiation Therapy Precisely Delivered

Radiation therapy can be highly effective in treating cancer, or alleviating symptoms in patients with untreatable advanced stage cancers. Approximately half of all cancer patients will receive radiation therapy at some point in their treatment, which uses externally or internally delivered x-rays, protons or other high energy particles to target and destroy cancer cells. While improved technological approaches have reduced healthy tissue deterioration, traditional radiotherapy still causes side effects that can be difficult for some patients to tolerate. In addition, traditional radiotherapy is unable to target more than one site of disease, limiting its utility for patients with metastatic cancer. However, traditional radiotherapy remains one of oncology’s most powerful treatment tools.

This novel approach to tumor treatment — targeted radionuclide therapy — is reengineering the use of radiation treatments in precision oncology and delivering a new class of cancer therapies. The goal of targeted radionuclide therapy development is to combine alpha-, beta- or gamma-particle emitting isotopes — or radionuclides — with peptides, antibodies, or small molecules, to develop therapies with high specificity for certain types of tumors. Delivered to the patient intravenously, targeted radionuclide therapies are designed to travel directly to the tumor to deliver therapeutic radiation with high precision. This precision is intended to focus delivery of the radiation to the tumor tissue while minimizing radiation exposure to normal tissue.

Targeted radionuclide therapies have the potential to deliver therapeutic doses of radiation with high specificity for certain types of tumors.

Targeted radionuclide therapies have the potential to deliver therapeutic doses of radiation with high specificity for certain types of tumors.

Theranostics: Seeing What we Treat — Treating What we See

Radionuclides can be delivered to tumors using precision targeting agents to both treat cancer and image a patient for cancer. Agents that can use one radionuclide to image tumors while using a different radionuclide to deliver cancer-killing radiation directly to tumors are known as “theranostics”. By replacing cancer-killing beta- and alpha-particle emitting radionuclides with other radionuclides, such as the positron-emitter gallium-68, a single highly effective targeting molecule of a targeted radionuclide therapy can be transformed into an imaging agent. Theranostic radionuclide imaging agents target the same cells and tissues as the accompanying therapeutic agents. This allows oncologists to image treatable cancer tissues more completely, select patients for therapeutic applications, see precisely where therapeutic agents will be delivered, and monitor the ability of the therapeutic agent to shrink tumors over time. Theranostics provide oncologists with novel and highly effective tools to create precision treatment strategies for their cancer patients.

Replacing a therapeutic radionuclide with an imaging-specific radionuclide allows the clinician to see where the therapeutic agent will be delivered.

Replacing a therapeutic radionuclide with an imaging-specific radionuclide allows the clinician to see where the therapeutic agent will be delivered.

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