Are there additional minimally invasive treatments for unresectable malignant liver masses?
Use of yttrium-90 ( 90 Y) microspheres is a newer treatment option that delivers concentrated radiation to unresectable hepatocellular carcinoma and metastatic disease. 90 Y, with a half-life of 64.5 hours, releases beta particles that radiate adjacent soft tissue with an average penetration of 2.5 mm. 90 Y microspheres have a diameter of 20 to 30 μm, which become trapped in the capillary beds of the intended masses and deliver a substantial dose of radiation specifically to these regions without the dangers of systemic radiation.
To safely deliver the dose of radiation to the targeted disease, hepatic angiography via the femoral artery is performed first. To safely map the perfusion and subsequent delivery area of 90 Y microspheres, 99m Tc-MAA is administered directly to the hepatic artery in the identical manner that the 90 Y microspheres will be delivered. Because 99m Tc-MAA particles are similarly sized compared with 90 Y microspheres, the biodistribution of these radiopharmaceuticals should be nearly identical. Using the images from 99m Tc-MAA, the biodistribution is assessed and a shunt fraction is calculated to assess potential unwanted systemic distribution, particularly to the lungs. If these images and calculations demonstrate a safe delivery of 99m Tc-MAA, then treatment with 90 Y microspheres is possible.