When cancer spreads, it sometimes instigates a grim and frustrating game of hide-and-seek – tucking away malignant cells in otherwise healthy tissue throughout the body. Traditional imaging can make it tough to pinpoint where the cancer is hiding and treat just those spots, sparing healthy cells.
Our nuclear medicine physicians in the Department of Radiology and a multidisciplinary team of cancer experts are using a new molecular imaging and treatment technology to do just that.
Called theragnostics – a combination of therapy and diagnostics – the two-pronged approach enables us to precisely seek, find, and destroy metastatic cancer cells by combining advanced imaging techniques with targeted, injection-based molecular therapy that locally emits energy in the form of radiation to kill the cancer cells by breaking their DNA.
UT Southwestern is home to the first Society of Nuclear Medicine Molecular Imaging-designated comprehensive radiopharmaceutical therapy center in North Texas – and we are one of only a few medical centers in the area offering theragnostics for specific types of metastatic cancer that fail to respond to conventional treatment, such as chemotherapy.
The theragnostics concept builds on the 80-year history of using targeted radiopharmaceutical therapy for thyroid disease. It is a powerful tool in the fight against metastatic cancer, giving us the capacity to personalize potentially curative treatment and improve patient outcomes and quality of life. Theragnostics is in the early stages of routine clinical use, but at UT Southwestern we offer all approved agents for this leading-edge technology and plan to continue expanding our uses, individualized to our patients’ needs.
Who might be a candidate for theragnostics?
Cancer cells express unique molecular markers, making them different from normal cells. Some blood markers that tell us there is remaining cancer in your body include thyroglobulin in thyroid cancer, prostate-specific antigen (PSA) in prostate cancer, and chromogranin A in some neuroendocrine tumors.
If you have elevated levels of these proteins in your blood, there may be cancer cells hiding in your body. Upon observing higher-than-normal levels of these blood markers, we can perform scans with specific radiopharmaceuticals that bind to those “targets” on the cancer cells. After seeking and finding metastatic cancer cells, we can then precisely focus our treatment to target these cells.
Theragnostics offers a chance to improve quality of life – and potentially cure – some metastatic cancers. Conditions we currently treat with theragnostics include:
- Thyroid cancer
- Prostate cancer
- Neuroendocrine tumors
- Metastatic meningioma
- Pheochromocytomas and paragangliomas
- Cancer-related bone pain
These cancers and medical conditions have been shown to have characteristic targets that we can home in on to apply this advanced approach. The number of identified targets grows each year – and so does the number of cancers we can effectively treat with theragnostics.
How does theragnostics work?
The theragnostic process has two phases. In the diagnostic phase, we locate the cancer cells by injecting into your bloodstream a radiopharmaceutical called a molecular imaging probe. Also called a radiotracer or radiopharmaceutical, this molecule has two jobs:
- Detect and latch on to cancer cells that express the target
- Emit a low amount of radiation once it finds those cells, so they are visible on specialized images known as positron emission tomography (PET) or single-photon emission computed tomography (SPECT) scans
Depending on the radiotracer it can take an hour or more for the radiopharmaceutical to distribute through the body and bind to the cancer cells before we take the imaging scan. Then we review the images and, depending on the results, talk with you and your referring doctor about the desire to proceed with treatment.
In the treatment or therapy phase, our nuclear medicine physicians inject a different radiopharmaceutical into your blood to seek and find cancer cells. This radiopharmaceutical is made up of the same part for binding to the cancer cell but has a different radiation emitting part. This type is a stronger form of radiation that kills cancer cells while minimizing damage to the surrounding tissue. The injection may only take a few minutes or up to 30 minutes depending on the treatment. After the injection you’ll stay for a few minutes to a few hours of observation before going home.
Over the next few days and weeks, the radiation eliminates cancer cells. Radiopharmaceutical material that does not bind to the cancer cells exits through your bodily fluids. Most treatment plans include 6-8 sessions of radiopharmaceutical therapy with an interval of 4-8 weeks between each dose. Depending on how the cancer responds, we may recommend another round of treatment. Our nuclear medicine team will guide you through each step of the theragnostic process, working closely with your medical, radiation, and surgical oncology team to adjust your treatment plan, if needed.
Side effects with theragnostics vary depending on the specific treatment but in general they are similar to those of other cancer treatments, such as fatigue, reduced appetite, or nausea. However, in most patients, side effects are temporary and well tolerated. Our physicians will be sure to tell you about potential side effects for your specific treatment.
There may be a few days or weeks between the diagnostic and treatment phases, depending on your condition and the availability of the radiopharmaceutical drug. UT Southwestern produces one formulation for the diagnostic phase of prostate cancer theragnostics on site, but most compounds come from radiopharmaceutical suppliers.
The future of theragnostics
Interest in newer targeted therapeutics is exploding as our understanding of molecular markers of metastatic cancer increases. We are discovering more targets every year, and as we do, new radiopharmaceuticals can be developed to treat more patients.
Researchers are finding that some targets are not unique to one type of cancer. For example, prostate-specific antigen (PSA) shows up in prostate cancer as well as certain forms of kidney cancer and some somatostatin receptors in neuroendocrine tumors also are expressed in meningiomas, which are tumors in the brain or spinal cord. So, we expect that theragnostics will be approved to target more types of metastatic cancers in coming years.
Also on the horizon are radiopharmaceuticals that are more efficient at breaking up and destroying the cancer cells’ genetic makeup. Increased efficiency means more effective therapy with less radiation dosage. In clinical trials or laboratory studies, physicians and scientists are also studying the potential effectiveness of incorporating immunotherapy into the theragnostic approach for metastatic HER-2 positive breast cancer, lymphoma, and other cancers as well as combining external beam radiation and theragnostics.
UT Southwestern is proud to offer our patients advanced therapies like theragnostics that are personalized to their specific condition and needs. To learn whether you or a loved one might be a candidate, call 214-645-8300 or request an appointment online.