Scout Dose of Resin Microspheres

This study looks at a liver cancer treatment called radioembolization and tests a new, possibly more accurate way to check if the treatment is safe for a patient's lungs.

Radioembolization is a procedure where tiny beads containing a radioactive substance (yttrium-90) are injected into the arteries that feed a liver tumor. These beads lodge mainly in the tumor and deliver radiation directly to it, while sparing most of the normal liver. However, some of these beads can bypass the liver circulation and travel to the lungs. If too many reach the lungs, they can cause serious radiation damage called radiation pneumonitis.

To avoid this, doctors currently perform a "test run" before the real treatment. They inject a different particle called MAA into the liver artery and then do nuclear medicine scans to see how much of it goes to the lungs versus the liver. This percentage is called the lung shunt fraction. If the lung shunt is 20% or higher, radioembolization is not done; if it is between 10% and 20%, the decision depends on tumor size. The actual treatment usually happens 1-2 weeks after this test.

MAA particles are similar in size to the treatment beads but not identical; some are smaller. Because of this, MAA may slightly overestimate how much of the treatment dose would really go to the lungs. Also, MAA is fully imported and has had periods of supply problems worldwide. For these reasons, there is a need for another, more accurate and more reliable way to measure lung shunt.

The LASER study tests an approach called a "scout dose." In this method, doctors take a small amount of the actual treatment beads (SIR-Spheres, a resin yttrium-90 microsphere product) and inject a low radioactive dose (0.56 GBq) into the liver artery on the day of treatment. They then perform a PET/CT scan and calculate how much of this scout dose went to the lungs and how much stayed in the liver. Because the scout dose uses the same type of beads as the real treatment, it may give a more accurate picture of the true lung shunt.

The study will enroll 30 adult patients who have liver tumors (liver cancer, intrahepatic cholangiocarcinoma, or liver metastases) and are already scheduled to receive radioembolization. All participants must have good liver function (Child-Pugh A), good performance status (ECOG 0-1), and an MAA-based lung shunt fraction below 20%. They also need to meet standard blood test criteria and have a life expectancy of at least three months.

Each patient first undergoes the usual work-up: liver artery angiography, MAA injection, and nuclear scans, which are used to plan the treatment dose. One to two weeks later, on the treatment day, the patient has another angiogram, receives the 0.56 GBq scout dose into the liver artery, and has a scout PET/CT scan while the catheter is kept in place. After calculating the lung shunt from the scout dose, the patient is brought back to the angiography room and receives the planned treatment dose, reduced by the amount already given as the scout dose. The next morning, a treatment Y90 PET/CT scan is performed.

The main measurement of interest is the lung shunt fraction calculated three different ways: from the initial MAA scan, from the scout Y90 PET/CT, and from the treatment Y90 PET/CT. The researchers will compare how closely these three values agree. They will also look at how much radiation the tumor and normal liver receive (tumor dose, normal liver dose) and the radiation dose to the lungs, again using all three imaging methods.

Patients will be followed for one year with regular clinic visits, blood tests, and CT or MRI scans according to usual care. The study will carefully record side effects such as fatigue, pain, poor appetite, and more serious problems like liver failure or radiation pneumonitis, and grade them using a standard international system (CTCAE v5.0). The researchers expect that adding the scout dose and extra scan will lengthen the procedure by about two hours and cause some discomfort from lying down longer, but they do not expect a major increase in serious risks compared with standard treatment.

By the end of the study, the team aims to show whether the scout dose method can safely and accurately replace or complement the traditional MAA-based test. If successful, this could improve the precision of radioembolization planning and offer a reliable alternative when MAA is not available