By Lynda De Widt
In the 1960's, scientists discovered a form of cancer therapy called radioembolization, which utilizes microscopic radioactive spheres delivered through a blood vessel to reach a tumor and kill tumor cells. "Think of it as a tiny radiation bomb that's delivered directly where it's most needed," says Beau Toskich, M.D., an interventional radiologist who specializes in interventional oncology at Mayo Clinic in Florida.
In the previous decades, radioembolization had been used as a palliative treatment option (read related patient story) to slow progression of advanced liver cancer in patients who were not candidates for curative therapies and had typically undergone chemotherapy. Now, Dr. Toskich and colleagues are conducting research to revisit this technology, finding new ways to maximize its capabilities.
For most cancer types, radiation therapy originates outside the body, penetrating through skin, bone, and adjacent organs to reach malignant cells, which can limit the amount of radiation that can be given safely. But many liver tumors have a unique property that makes radioembolization possible: they base their blood supply almost entirely on a few arteries that normally nourish portions of the liver. Thus, if radioembolization is delivered only through liver arteries that are responsible for supplying the tumor, higher doses of radiation can be safely administered. “It's like a contained nuclear explosion that surrounds the cancer, while the untreated liver has little to no radiation exposure" Dr. Toskich says.
The research of Dr. Toskich's team centers on mapping specific liver blood supply territories, using small catheters and mini-CT scans to analyze the blood vessels responsible for nourishing an individual's tumor. After mapping is complete, the patient typically receives treatment during a single outpatient session. As the radiation takes effect over the course of several months, the liver uses its inherent regenerative abilities to recover from the small portion of itself that had been treated alongside the tumor. In another project, Dr. Toskich is also working with Kabir Mody, M.D., to determine whether radioembolization can stimulate the body's immune response in order to fight liver cancer.
With higher radiation doses enabled by this more precise radioembolization approach, tumors are showing promising response in early research. As a result, the team is optimistic about its ability to increase the number of liver cancer patients who are candidates for tumor-removal surgery, either through transplantation or resection, or with radioembolization as the sole therapy in select circumstances. "We are finding that in patients who received liver transplantation after high dose radioembolization, about half of targeted tumors show complete cell death and over 95 percent show extensive treatment response," says Dr. Toskich. "Certain tumors are being eradicated by radioembolization, which used to only be capable of slowing the progression of liver cancer when other treatments were not an option."
"Radioembolization has an important role in controlling tumor growth in patients with liver cancer while they await a transplant," says Tushar Patel, M.B., Ch.B., dean for research at Mayo Clinic in Florida, who is collaborating on this work. "We think that it may also be used as curative treatment in patients with very early liver cancer. Mayo's extensive efforts in liver cancer research, combined with our comprehensive interdisciplinary care capabilities, are helping us develop unique treatment strategies."