FDA Approves TheraSphere Y-90 Glass Microspheres for Hepatocellular Carcinoma

SUMMARY: The FDA on March 18, 2021 approved TheraSphere Y-90 Glass Microspheres, developed for the treatment of patients with HepatoCellular Carcinoma (HCC). The American Cancer Society estimates that for 2021, about 42,230 new cases of primary liver cancer and and intrahepatic bile duct cancer will be diagnosed in the US and 30,230 patients will die of their disease. Liver cancer is seen more often in men than in women and the incidence has more than tripled since 1980. This increase has been attributed to the higher rate of Hepatitis C Virus (HCV) infection among baby boomers (born between 1945 through 1965). Obesity and Type II diabetes have also likely contributed to the increasing trend. Other risk factors include alcohol, which increases liver cancer risk by about 10% per drink per day, and tobacco use, which increases liver cancer risk by approximately 50%. HepatoCellular Carcinoma (HCC) is the second most common cause of cancer-related deaths worldwide, and majority of patients typically present at an advanced stage. The prognosis for unresectable HCC remains poor and one year survival rate is less than 50% following diagnosis.

Patients with HCC, with disease confined to one lobe of the liver often undergo liver resection if feasible, and liver transplantation when HCC is associated with chronic liver disease and cirrhotic livers. Other liver-directed therapies include ablative modalities such as SBRT (Stereotactic Body Radiation Therapy), Cryoablation, RFA (RadioFrequency Ablation), as well as Trans Arterial ChemoEmbolization (TACE) and Selective Internal Radiation Therapy (SIRT), also referred to as radioembolization. HepatoCellular Carcinoma’s derive their blood supply almost exclusively from the hepatic arteries, whereas the liver has a dual blood supply from the portal vein (75-80%) and hepatic arteries (20-25%). By taking advantage of the differential blood supply of hepatic tumors, chemo and radioembolization can be targeted to the tumor tissue, minimizing damage to the surrounding normal liver parenchyma.

TheraSphere treatment is a type of SIRT with low toxicity, and is comprised of millions of microscopic glass beads containing radioactive yttrium (Y-90), which is delivered to liver tumors via a hepatic arterial catheter, and results in minimal radiation exposure to surrounding normal liver parenchyma.

LEGACY trial is a single-arm, multicenter, retrospective study designed to evaluate the safety and efficacy of Yttrium-90 (Y90) glass microspheres in patients with unresectable solitary hepatocellular carcinoma (HCC). The objective of this study was to assess the Objective Response Rate (ORR) and Duration of Response (DoR) following treatment with Yttrium-90 (Y90), and the objective of the analyses presented was to evaluate ORR, DoR, and Overall Survival (OS) by transplant/resection status (neoadjuvant therapy with the intent to bridge patients to transplant or resection), and to compare these outcomes with patients who did not go on to transplantation/resection after receiving treatment with Y90. This study included 162 patients with Child-Pugh A and Barcelona Clinic Liver Cancer (BCLC) A or C disease, with unresectable solitary liver lesion that was 2-8 cm. The median patient age was 66 yrs and patients with portal vein thrombosis or extrahepatic disease were excluded. No prior liver transplantation, resection, locoregional treatment or systemic therapy was allowed. Primary efficacy endpoints included Objective Response Rate (ORR) and Duration of Response (DoR). ORR included patients who achieved either a Complete response or Partial Response, and response was determined by Blinded Independent Central Review (BICR). Secondary endpoints include Overall Survival (OS) and number and type of subsequent treatments, including transplantation and resection.

This study met both Primary endpoints and the ORR was 72.2% at 4 weeks and DoR (more than 6 months) was 76.1%. The median follow up for all 162 patients enrolled was 29.9 months and 3-year OS was 86.6%. Among the 45 of the total 162 patients who received neoadjuvant Y90 treatment, 21% went on to transplantation and 7% went on to have resection. In the neoadjuvant treatment group, ORR was 100%, DoR (more than 6 months) was 30.6% and 3-year OS was 93%. Liver function as determined by levels of albumin and bilirubin were maintained in over 85% of patients.

It was concluded that treatment of solitary unresectable HCC with Y90 glass microspheres, performed as an outpatient procedure, resulted in significant ORR, DoR, and OS, both as neoadjuvant therapy prior to transplantation/resection and as treatment in non-surgical candidates.

Use of yttrium-90 (Y90) glass microspheres (TheraSphere) as neoadjuvant to transplantation/resection in hepatocellular carcinoma: Analyses from the LEGACY study. Lewandowski R, Johnson GE, Kim E, et al. DOI: 10.1200/JCO.2021.39.3_suppl.300 Journal of Clinical Oncology 39, no. 3_suppl (January 20, 2021) 300-300.