Transarterial Radioembolization for Early, Localized, Inoperable Hepatocellular Carcinoma (HCC) Using Holmium-166

Hepatocellular carcinoma (HCC) is the most common form of liver cancer and usually occurs in people with pre-existing liver damage, such as cirrhosis or hepatitis B or C. Symptoms are very nonspecific, such as fatigue and unintentional weight loss, which is why the diagnosis is often made only during routine checkups. In advanced stages, the disease may present with tenderness in the upper abdomen, yellowing of the skin and the whites of the eyes (icterus), and an increase in abdominal girth.

Depending on its spread, HCC is classified into different tumor stages. An early, localized stage means that the tumor is small, confined to the liver, and has not invaded blood vessels or other organs. Treatment options include surgery, liver transplantation, or local therapies such as radiofrequency ablation or transarterial radioembolization (TARE). The decision regarding treatment is made on an individual basis based on criteria such as infection status, tumor stage, current liver function, and specific tumor characteristics. In many cases, surgery is the preferred option.

However, if surgery is not possible at an early stage, local tumor control becomes the primary goal, and TARE may be used. In TARE—sometimes also called SIRT (selective intra-arterial radioembolization)—radioactive microparticles are injected directly into the blood vessels supplying the tumor. The microspheres block the blood supply to the tumor and also emit short-range radiation that kills the surrounding cancer cells. Holmium-166 microspheres have been approved for several years now and, compared to earlier procedures (e.g., yttrium-90), have demonstrated that the radiation targets the tumor tissue more precisely and that side effects can be reduced due to the faster release of radiation. Nevertheless, the treatment can damage healthy liver tissue.

The goal of the HOMIE-166 study is to investigate the efficacy of holmium-166 at the optimal dose for patients. It is an open-label Phase II study without a control group, which means that all study participants receive the same treatment and are aware of it.

Initially, all study participants receive a test dose (“scout dose”) to determine whether the procedure is suitable for them. If so, the actual treatment with Holmium-166 microspheres is administered. The primary endpoint of the study is the objective tumor response rate—that is, whether the tumor shrinks or changes as a result of the individual treatment dose. This will be monitored using imaging techniques over a five-year period.

To participate, patients must be at least 18 years old and have early-stage, inoperable hepatocellular carcinoma. The tumor may be up to 8 cm in size, or there may be up to three tumors in the liver, each with a maximum diameter of 5 cm. All study participants must have good liver function. Patients with cirrhosis above a certain severity level, tumor spread outside the liver, or a life expectancy of less than six months are not eligible to participate. Previous cancer treatments or a prior liver transplant are also exclusion criteria.