Theranostics Delivers a One-Two Punch

Many of us are familiar with the most common strategies for treating cancer: surgery, chemotherapy and radiation therapy. But in the past two decades, new, more targeted treatments have been developed.

One such innovation combines diagnostic testing with therapy to form a type of treatment called theranostics. This therapy, available at Siteman Cancer Center, based at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, uses specially engineered radioactive tracers, called radiopharmaceuticals, in combination with advanced imaging techniques.

Working together, the two elements not only find and map cancer cells throughout the body, they also serve as a beacon, lighting a path that cancer-destroying drugs can follow. It’s a one-two punch delivered directly to cancer cells.

“The power behind radiopharmaceuticals is their ability to maximize the tumor radiation dose while minimizing collateral damage to healthy tissues,” said Washington University radiation oncologist Hyun Kim, MD, co-director of the Theranostics Center at the School of Medicine.

“While traditional, external beam radiation must pass through healthy tissue to reach the tumor, radiopharmaceuticals travel directly to the tumors, even when they are distributed throughout the body,” said Kim, who also is an associate professor of radiation oncology at the School of Medicine. “Since the radiation dose only travels millimeters, this allows radiopharmaceuticals to be a powerful, focused radiation treatment option.”

The university’s clinical theranostics program, a collaboration between Mallinckrodt Institute of Radiology and the radiation oncology department, recently received designation as a Comprehensive Radiopharmaceutical Therapy Center of Excellence (RTCOE) by the Society of Nuclear Medicine & Molecular Imaging. The distinction signifies leadership in the field, with experience administering multiple radiopharmaceutical therapies, established care teams in specific disease areas and a focus on research.

Washington University nuclear medicine radiologist Vikas Prasad, MD, the program’s other co-director, said theranostics “operate the way a key and lock do.”

“We design a radiopharmaceutical that looks for a certain biomarker on the surface of cancer cells and, once found, the radiopharmaceutical then inserts itself into that biomarker,” said Prasad, who also is an associate professor of radiology at the School of Medicine.

After the radiopharmaceutical tracer is administered via injection into the bloodstream, specialists use scans to visualize the cancer cells detected by the tracer. “When we can see what we need to treat,” he said, “we can then treat what we see.”

Jeff Michalski, MD, the Carlos A. Perez Distinguished Professor and vice chair and director of clinical programs at the School of Medicine, adds: “We take SPECT/CT (single photon emission computerized tomography/computerized tomography) scans of the patient over a period of days.”

That series of images, he notes, “allows us to determine whether there has been uptake of the tracer into the cells. We can also see how quickly the tracer disappears.” Armed with that knowledge, he and colleagues can predict whether the patient may benefit from treatment with a cancer-killing agent and can identify the amount of drug needed.

Any cancer cell that has a known biomarker on its surface potentially can be treated with radiopharmaceuticals, provided there is sufficient blood supply to the site to deliver the drugs.

Farrokh Dehdashti, MD, a professor of radiology and senior vice chair and director of the Division of Nuclear Medicine at the School of Medicine, has studied novel radiotracers for three decades, conducting early clinical trials of several tracers developed at the university.

“The field of theranostics has provided patients with therapy that allows for personalized management and treatment of their cancers,” she said. “This type of therapy can be effective and can improve patient outcomes, even when the disease is very advanced.”

Michalski, who also is medical director of clinical trials at Siteman, served as principal investigator for clinical trials evaluating the first targeted radiopharmaceuticals for prostate cancer. Right now, the use of radiopharmaceuticals to treat prostate cancer is approved only for patients with metastatic, castration-resistant prostate cancer who have failed other treatments.

“As we move through more clinical trials, we want to determine whether we can use these radiopharmaceuticals earlier and prevent people from progressing to later stages of disease,” he said. “We’ll also be evaluating whether we can customize the dosage of drugs to each patient based upon their disease progression as seen in imaging.”

Theranostic-based treatment doesn’t work for all patients with cancer. Currently, it’s available only as a third or fourth line of cancer treatment, after other options have failed. Also, use of radiopharmaceuticals to treat cancer is approved only for prostate cancer, thyroid cancer and the treatment of neuroendocrine tumors. And, despite the proven success of theranostics’ ability to locate and destroy cancer cells, in one-third of patients, the cells don’t take up the designed tracer, meaning that administration of a cancer-killing drug likely won’t succeed.

That’s why more research is needed. Already, U.S. trials are evaluating radiopharmaceuticals that can detect biomarkers for more cancers, including leukemia, brain tumor, liver cancer, melanoma and breast cancer.

“In one to two years, we’ll see theranostics become an even stronger option for cancer treatment,” Prasad said. “And in five years, I envision its use in 10 or more cancer types, as well as its use as a therapy in combination with immunotherapy treatments.

“It’s exciting to see how rapidly this field is evolving,” Prasad added. “The gate is wide open.”

To make an appointment at Siteman, call 314-747-7222 or 800-600-3606, or visit siteman.wustl.edu.