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Reston, VA (March 31, 2025) — The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is proud to recognize World Theranostics Day on March 31, 2025. Theranostics evolved from the early days of nuclear medicine, when radioactive isotopes were first used to image internal organs and to treat disease. Over the following decades, as nuclear medicine imaging and therapies advanced, the approach of combining diagnostics with therapy—aimed at tailoring treatment to individual patients—gradually coalesced into what we now call “theranostics.”
Unlike imaging methods like x-ray or CT, which reveal anatomic detail, nuclear medicine imaging reveals the body’s functional processes at the cellular and molecular level. This ability to image function, rather than just anatomy, is critical for diagnosing complex conditions such as cancer, cardiovascular disease, and neurological disorders. Using advanced imaging techniques such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), small doses of radioactive material are administered to the patient to produce highly detailed images of physiological activity. These images are essential tools for diagnosing disease, evaluating disease progression, and assessing treatment response.
The cell-targeting ability of nuclear imaging agents offers an excellent means of delivering treatment. In fact, one of the earliest applications of nuclear medicine—radioiodine (I-131) therapy—has been a highly successful treatment of thyroid disorders and hyperthyroidism for more than half a century. In this therapy, radioactive iodine is introduced into the body and absorbed by the thyroid cells or thyroid cancer cells, where it kills them. Since that time, radionuclide therapy has expanded to address many other conditions, including several types of cancer.
Recently, a groundbreaking approach called theranostics has emerged that combines nuclear medicine diagnostics and therapy. Theranostics is based on the use of the same targeting molecule to both diagnose and treat a disease. The molecule is labeled with an imaging radionuclide to diagnose the disease using PET or SPECT imaging and a therapeutic radionuclide to treat the disease. This allows the physician to deliver a personalized, highly targeted therapy directly to tumors while minimizing damage to nearby healthy tissues.
Recent developments in theranostics have been transformative in the treatment of prostate cancer and neuroendocrine tumors. In prostate cancer, the diagnostic and therapeutic target is prostate-specific membrane antigen (PSMA), which is found on the surface of prostate cancer cells. The PSMA targeting molecule is labeled with gallium-68 or fluorine-18 to image the tumor using PET; and after the tumor is visualized and the presence of the PSMA target verified, the same molecule is labeled with lutetium-177 to treat the tumor.
Theranostics works similarly with neuroendocrine tumors (NETs). Instead of PSMA, NET cells produce somatostatin receptors. These receptors can be visualized with a PET radiopharmaceutical such as gallium-68-DOTATATE, and lutetium-177-DOTATATE is used as the therapeutic radiopharmaceutical.
One of the great advantages of nuclear medicine procedures is their safety and non-invasive nature. The amount of radioactive material used in diagnostic imaging is quite small, and the resulting radiation dose is similar to that from an x-ray or CT scan. Similarly, the radiation exposure from therapeutic nuclear medicine procedures is comparable to that from external beam radiation therapy. Overall, the risks from nuclear medicine procedures are very low, especially when considering their tremendous benefits, including the early detection of disease and the ability to tailor treatment plans for each patient.
Personalized healthcare is a defining trend in modern medicine, and nuclear medicine plays a pivotal role in this trend. There are many exciting recent developments in nuclear medicine that are now in clinical trials, including the use of alpha-emitting radionuclides such as actinium-225 and lead-212 for treating prostate cancer and neuroendocrine tumors. Alpha-emitting radionuclides can deliver a higher radiation dose directly to tumors while delivering a lower radiation dose to surrounding tissue. In addition, there are exciting developments in the clinical pipeline for the treatment of other malignancies, including breast cancer and brain tumors. These developments are reflected in projections for the radiopharmaceutical market, which is expected to see substantial growth in the coming years as drugmakers continue to invest in these innovative treatments.
The future of nuclear medicine, molecular imaging, and theranostics is bright! As SNMMI celebrates World Theranostics Day, it is clear that nuclear medicine and molecular imaging will continue to drive major advances in healthcare. By improving the ability to detect disease, to monitor response to therapy, while also providing more personalized ways to treat disease, nuclear medicine is shaping the future of medicine and improving patient outcomes.