Tolerance of the liver to the effects of yttrium-90 radiation

There are no reliable data documenting the tolerance of the human liver to ionizing radiation from a continuous Yttrium-90 source. As Yttrium-90 incorporated into microspheres is being used to treat patients with liver cancer, it is imperative that the tolerance of the human liver to this form of radiation damage be determined. Four patients with metastatic liver cancer were treated with Yttrium-90 to deliver radiation doses above that considered tolerable when given by conventional external sources. Patients were monitored with serial estimations of liver function tests and between 7 and 9 months after treatment liver biopsies were performed. Histological examination of the liver biopsies confirmed only minimal changes in the normal liver parenchyma. These data indicate that the human liver may tolerate relatively large radiation doses when delivered by Yttrium-90 microspheres embedded in the liver parenchyma as a number of discrete point sources.