Effect of starch microspheres on the passage of labelled erythrocytes and a low molecular weight marker through the liver.

Abstract

Degradable starch microspheres (DSM) injected intra-arterially together with cytostatic drugs increase the regional uptake of the drug and as a result reduce the systemic drug concentration. Previous studies have indicated that fixed doses of DSM result in different degrees of vascular occlusion and therefore variable systemic concentration of the co-injected drug. Continuous registration of the systemic concentration of 99Tcm-hydroxymethylene diphosphonate (99Tcm-HDP) co-injected intra-arterially with DSM was earlier used to monitor treatment sessions and to optimize the dose of microspheres. Further to investigate the mechanism of DSM-induced retention, the effect of DSM on the passage of this low molecular weight marker and of labelled erythrocytes (a marker confined to the blood vessels), was compared in 10 patients with liver metastases. DSM reduced the amount of 99Tcm-HDP passing through the liver by 6 to 47 per cent while the amount of erythrocytes eventually passing the liver was much less reduced (0-14%). The rate of passage, however, was significantly reduced for both labelled markers. These results indicate that substances retained by co-injection of DSM are not to a significant extent lodged within the blood vessels but diffuse into extra-vasal tissue compartments.