Boston Scientific Corp.'s Therasphere Y-90 glass microspheres received a PMA for treatment of patients with unresectable hepatocellular carcinoma (HCC). The radioembolization technique has been used in more than 70,000 patients under a humanitarian device exemption over the last 20 years. The U.K.'s NICE also recently recommended Therasphere for treatment of patients with HCC.

“Treatment with Therasphere has been increasing each year in the U.S., and in 2020 was used in nearly 8,000 patients,” Peter Pattison, Marlborough, Mass.-based Boston Scientific’s president of interventional oncology, peripheral interventions, told BioWorld. “However, the requirement of an [institutional review board] approval was restrictive and with this approval and elimination of the humanitarian device exemption (HDE) limitations we look forward to expanding access to this life-prolonging therapy for a greater number of patients.”

HCC is the third leading cause of cancer-related death worldwide, accounting for more than 500,000 cases annually. In the U.S., it is one of only three types of cancer that increased in incidence and mortality over the last decade, according to the CDC. While the incidence rate plateaued after 2015 as more effective and tolerable treatments for hepatitis C virus, long the leading cause of HCC in the U.S., came on the market, it has resumed rising as cases of fatty liver disease have increased along with growing rates of obesity. About 32,000 new cases of HCC are diagnosed each year.

The five-year mortality rate for HCC remains under 19%, despite an increasing number of new systemic therapies. The only curative treatments remain resection and transplantation, but many patients are diagnosed too late to qualify for those options. Therasphere is a type transarterial radioembolization (TARE) or selective internal radiation therapy (SIRT) that uses yttrium-90 (Y-90) to reduce tumor burden and can improve patient health and characteristics sufficiently to qualify them for transplantation.

While other embolization types can be used for liver tumors, Therasphere offers a single, outpatient treatment of about an hour and can be used in a wide range of anatomical structures and locations.

With the new approval, “Therasphere will now be accessible to nearly half of patients with hepatocellular carcinoma in the U.S.,” Pattison added.

Study results

Therasphere uses millions of microscopic glass beads that contain Y-90, a radioactive isotope. The treatment penetrates about one centimeter into the body, limiting the damage the beads can do to surrounding tissue. The radioactive beads are delivered directly to liver tumor vasculature via transfemoral catheterization of the hepatic artery. The treatment benefits from the unique structure of blood supply to the liver which ensures that blood supply to liver tumors derives almost entirely from the hepatic artery, while most other liver tissues obtains its blood supply via the portal vein.

The FDA made the decision based on the results of the Legacy trial, which showed that all patients treated with Therasphere experienced elimination of all lesions or at least a 30% reduction in target lesion diameter with up to two treatments. Of those who had the treatment followed by transplantation or resection, 93% survived at least three years. The objective response rate at four weeks was 72.2% and that response lasted for at least six months in more than three out of four responders.

“[W]e found that patients with early and advanced HCC exhibited very high response rates as well as clinically meaningful durations of response and survival, establishing Therasphere as a standard treatment for this patient population," said Riad Salem, interventional radiologist at Northwestern Memorial Hospital and principal investigator of the Legacy trial. "The trial results, which have been accepted for publication in Hepatology, produced one of the most comprehensive databases for Therasphere, empowering physicians to make informed, data-driven decisions for their patients."

"We expect to continue to focus our efforts on bringing this treatment to more patients, both by planning a randomized trial to study the combination of Therasphere and immunotherapy in patients with HCC not eligible for curative treatments, as well as further investigating the therapy for different cancer segments, including prostate and brain,” Pattison noted. He expected the immunotherapy and Therasphere trial to begin enrollment later in 2021.