Pathologic response and microdosimetry of (90)Y microspheres in man: review of four explanted whole livers

Radioactive microsphere (90)Y therapy is increasingly used for primary and metastatic solid tumors in the liver. We present an analysis of 4 explanted livers previously treated with (90)Y microsphere agents (glass or resin). One tumor nodule was analyzed with submillimeter three-dimensional microdosimetry.

Four patients received hepatic artery delivery of (90)Y microspheres for unresectable hepatocellular and colon cancers. Whole livers were explanted as part of lifesaving cadaveric transplant in 2 patients with hepatoma. These patients had received glass microspheres as a procedural bridge to transplant. Autopsy was performed on 2 patients with colon cancer who died of progressive metastatic disease and who had been treated with resin microspheres. Complete pathologic review was performed on each whole liver, including estimation of the response of the tumor to therapy, distribution of microspheres in the tumor and normal liver tissues, and normal-tissue radiation response. A biopsy taken from the edge of a tumor nodule was sectioned serially for three-dimensional radiation dosimetry analyses. Three-dimensional microsphere coordinates within the biopsy specimen were used to calculate dosage using a three-dimensional dose kernel. Isodose coverage of tumor and normal liver areas and total dose delivered were determined.

Preferential and heterogeneous deposition of microspheres was noted at the edge of tumor nodules compared with the center portion of the tumor or normal liver parenchyma. Both glass and resin microspheres delivered high cumulative doses to the tumor, which varied from 100 Gy to more than 3000 Gy. No veno-occlusive disease or widespread radiation hepatitis was seen.

Microsphere ((90)Y) therapy delivers high numbers of spheres with resulting high total doses of radiation, preferentially in the periphery of tumors. Normal liver parenchyma showed little radiation effect away from the tumors. Heterogeneous high-dose regions in the tumor were produced by both glass and resin microspheres.