Y-90 Radioembolization - Principle, Procedure, Criteria, and Risks

Introduction:

Y-90 radioembolization uses yttrium-90 embedded in the embolic agents to treat hepatic (liver) cancer. This procedure is also called TARE-Y90 (transarterial radioembolization with yttrium-90). Y-90 is used to treat primary liver cancer such as hepatocellular carcinoma (cancer originates in the liver), intra- hepatic cholangiocarcinoma (cancer originates in the bile ducts), and secondary hepatic tumors such as metastasis to the liver (cancer spreads to the liver from different body parts).

What Are the Embolic Agents Used in the Y-90 Radioembolization Procedure?

Embolization is a medical procedure that uses tiny particles, such as small gelatin sponges or beads (embolic agents), to block the blood vessels. Embolic agents commonly used in Y-90 radioembolization are microspheres or glass beads containing yttrium-90. Yttrium-90 is a beta emitter that produces energy of about 0.9MeV. It can penetrate up to 2.5 mm. The half-life of Y-90 is about 64.2 hours. Y-90 is embedded in the microspheres of the size range from 20 to 60 microns. Y-90 is commercially available as Y-90-tagged glass and resin microspheres.

How Does the Y-90 Radioembolization Procedure Work?

• The Y-90 radioembolization procedure utilizes the advantage of a dual blood supply of the liver. The liver has its blood supply from an artery (hepatic artery) and a large vein (portal vein). The normal liver cells receive about 75 percent of their blood supply from the portal vein and 25 percent of their blood supply from the hepatic artery.

• Tumor in the liver receives most of their nutrients and oxygen through the hepatic artery. Y-90 embedded microspheres are injected into the hepatic artery in a 3:1 to 20:11 ratio, which affects the tumor cells by releasing high-energy radiation and spares the healthy liver cells.

• When the embolization (blocking the artery) is done, the normal liver cells receive their blood supply from the portal vein.

How Is the Y-90 Radioembolization Procedure Performed?

Patients should undergo a CT (computed tomography) or MRI (magnetic resonance imaging) scan of the abdomen before the procedure to determine the tumor and liver volume.

Before the Y-90 radioembolization procedure, a hepatic arteriogram should be performed on the patients.

• Hepatic Arteriogram:

1. A hepatic arteriogram or arteriography is a procedure used to visualize the function and abnormalities of the arteries. This procedure is required to visualize the collateral (additional but secondary) arteries of the stomach and duodenum from the hepatic artery. The collaterals are blocked by closing them with a small coil of wires.Finally, they will inject the microspheres into the catheter the same as the radioembolization procedure, which helps in calculating the dosage of microspheres that reaches the lungs.
2. This helps to adjust the dosage to prevent lung damage.

• Y-90 Radioembolization:

1. Y-90 radioembolization is usually done by a specialized doctor called an interventional radiologist. Patients are asked to lie on the procedure table.
2. Then, the nurse or doctor will insert an intravenous (IV) line into the hand to deliver the sedative to make them feel relaxed and sleepy. This procedure requires moderate sedation. Children may require general anesthesia to help them hold in place and be comfortable during the procedure. The patient’s heart rate, BP (blood pressure), oxygen level, and pulse rate will be monitored throughout the procedure.
3. During this procedure, the interventional radiologist will make a small incision at the site. Under the guidance of X-ray, usually fluoroscopy (X-ray video), they insert a thin tube called a catheter through the sterilized area of the skin into the femoral artery in the groin and advance it to the liver.
4. Once the catheter is placed in the branches of the artery that supplies the tumor, Y-90 is delivered in the form of microspheres or glass beads through the catheter and reaches the target site.
5. The microspheres release a high dose of radiation for the next 10 to 14 days, which directly affects the cancer cells of the liver by blocking the blood vessels.
6. The microspheres will eventually decrease in number by the time two weeks and are not visible after 30 days. The tiny particles of microspheres may remain in the liver, but it does not harm the liver cells.
7. After the radioembolization procedure, the doctor will remove the tube and apply pressure to stop bleeding from the site. They will use a closure device to seal the small hole in the artery. The incision in the skin will be covered with a dressing. This procedure usually takes an hour to complete. It may vary sometimes.
8. Patients may be instructed to stay in the hospital after the procedure between two to six hours. It depends on the type of artery which was accessed.

What Are the Criteria for Patient Selection in Y-90 Radioembolization?

• Patient age should be equal to or more than 18 years old.
• Total serum bilirubin level less than 2 mg/dL.
• Patients should be able to undergo the angiography procedure.
• Hepatocellular carcinoma patients who can not undergo surgical resection.
• The Eastern Cooperative Oncology Group (ECOG) performance status should be 0 to 2.
• Patients should be capable of coil embolization (a procedure that blocks the collateral blood supply by closing them with a small coil of wires).

What Are the Risks Associated With the Y-90 Radioembolization Procedure?

• Patients may feel slight pain while inserting a needle into the vein.
• There may be a risk of damage to the blood vessel, bleeding at the puncture site, and infection while placing the catheter inside the blood vessel.
• There might be a minimal or rare chance that embolization material reaches the wrong place and cuts off the blood supply to the normal tissue.
• As this procedure uses contrast material, there might be a chance of allergic reactions to contrast material.
• Even though antibiotics have been given during the procedure, there might be a risk of infection from skin incision after embolization.
• Patients may rarely experience some of the post embolization (after embolization) symptoms such as nausea, groin pain, and fever the next day. Medicines can help with these symptoms.
• Leukopenia (decrease in the count of white blood cells).
• Thrombocytopenia (decrease in the count of platelets).

Conclusion:

The primary role of radioembolization is killing the cancer cells by releasing high-energy radiation at a dosage of about 100 to 1000 + Gy. In TARE Y-90, the microspheres are smaller in size (20 to 30 microns) when compared to the particles of TACE [transarterial chemoembolization] (200 to 500 microns). Hence, it is less effective in embolization (smaller particle size). As Y-90 radioembolization uses greater radiation doses, the liver tumor cells respond well to the treatment. The side effects such as fever, tiredness, vomiting, nausea (urge to vomit), and abdominal pain are less often found in Y-90 radioembolization when compared to TACE (transarterial chemoembolization) and RFA (radiofrequency ablation).