Yttrium-90 (Y-90) has long been used to treat liver cancer. Researchers are exploring its potential to treat diseases in other sites, but a number of obstacles have made progress halting.
Y-90 radioembolization became popular for liver cancers because it is an extremely targeted therapy that can be delivered on an outpatient basis. Additionally, it has fewer adverse effects than other radiotherapies for similar cases, and it has had high response rates among patients. In fact, radioembolization may change some liver cancers from unresectable to operable. Such usage was predicted in 2014, and by 2016, early case studies were being published. In several cases, patients have undergone Y-90 radioembolization followed by resection of the diseased portion of the liver, with no evidence of disease in the remaining liver tissue, according to a 2016 report in Endovascular Today.
In this atmosphere of early promise, researchers at many institutions have been assessing the possibility of Y-90 radioembolization for diseases in other sites. Meningiomas, renal cell carcinomas and endocrine tumors have all been explored as promising areas for Y-90 radioembolization. The technique has also been considered for the treatment of noncancerous diseases, including enlarged spleen and obesity.
Its demonstrated effectiveness in hepatic cancer treatment since the early 1990s has fueled interest in Y-90’s potential. For example, Robert John Lewandowski, MD, FSIR, Associate Professor of Radiology, Medicine and Surgery and Director of Interventional Oncology at the Feinberg School of Medicine of Northwestern University in Chicago, has been using radioembolization for 16 years, treating more than 1,000 patients with primary liver cancer and more than 1,000 with metastatic cancer that has spread to the liver.
Expansion of treatment facilities has also inspired a wider focus on Y-90 radioembolization, says William S. Rilling, MD, FSIR, Professor of Radiology and Surgery and Vice Chair, Clinical Operations, in the Department of Radiology at the Medical College of Wisconsin.
“The number of treatment centers offering Y-90 has expanded throughout the world,” Dr. Rilling says. “As people have seen the benefits in situations with liver malignancy, it is natural to start thinking of where else we can use this tool. It’s not necessarily straightforward to extrapolate, but it’s a natural progression.”
Promising Patients and Sites
Selecting a patient or treatment site that will benefit from radioembolization relies on a rubric that is much the same no matter the part of the body involved, Dr. Lewandowski explains. Locally confined disease is especially amenable to this targeted therapy.
“Patients with hepatocellular carcinoma, the most common form of primary liver cancer, often have disease confined to the liver,” he says. “Locoregional therapies, such as radioembolization, are most often the preferred treatment.”
“[Radioembolization] really is a very elegant way to deliver high doses of radiation to targets, and that is the beauty of it.”
— William S. Rilling, MD, FSIR, Professor of Radiology and Surgery and Vice Chair, Clinical Operations, Department of Radiology at the Medical College of Wisconsin
For metastatic cancers, he explains, the same calculus makes treatment more complex.
“While locoregional therapies … often have a role in the treatment of these patients, timing with other treatments — chemotherapy or other local therapies such as surgery and external beam radiation — is mandatory,” he says.
The nature of the blood supply to the tumor is also important; highly vascular tumors with an isolated blood supply are considered most amenable to this treatment. With hepatic cancer, including metastatic cancers of the liver, the transcatheter intra-arterial delivery mechanism “takes advantage of the dual blood supply to the liver,” Dr. Lewandowski explains. However, that consideration limits possible uses of Y-90 in places other than the liver.
“We’d like to be able to do this on lots of tumors outside the liver,” Dr. Rilling says, “but the anatomy of the blood supply to other areas is not as isolated and not as straightforward.”
Meningiomas and renal cancer offer promising characteristics for treatment with Y-90, he continues.
“In [renal cancer] the anatomy is not so complex or risky, but in other tumors where it would be interesting to try to bring this therapy into play, the anatomy of the blood supply would make things pretty complicated,” he says. “To isolate the tumor from normal tissues is the bottom line.”
Radioembolization may also one day be used to treat noncancerous disease, Dr. Rilling says.
“One [nononcologic use] is for treating hypersplenism, where people have really big enlargement of the spleen,” he says. “Their blood counts will go way down; their platelet counts will go way down. Radioembolization may be a way to reduce the bulk of the spleen. You have less sequestration of blood elements in the spleen. Splenic embolization as done now can be painful and has a significant complication rate. … [T]his could potentially be a much more patient-friendly way to do that.”
Advantages of Y-90 Radioembolization
For the patient, radioembolization with Y-90 can be a convenient treatment with few side effects.
“The therapy is well-tolerated and can be done in … one or two treatment sessions,” Dr. Rilling says. “In the liver, for example, if people have bilobar metastases, we can do one lobe at a time in two sessions four weeks apart. From the patient perspective, the therapy has an endpoint, unlike chemotherapy, which may continue for weeks or months at a time.”
“The evolution of a treatment from experimental to standard of care depends on evidence provided by clinical trials,” says Dr. Lewandowski, who helped write the Society of Interventional Radiology guidelines for using Y-90 in metastatic cancers. “Endpoints such as safety and efficacy are most often considered; however, patient quality of life is becoming recognized as equally important to these outcomes. Radioembolization is an outpatient treatment with proven quality-of-life benefits over other, similar therapies.”