Increasing hepatic arterial flow to hypovascular hepatic tumours using degradable starch microspheres

The effect of degradable starch microspheres (DSM) on the intrahepatic distribution of a low molecular weight marker, Tc-99(m)-labelled methylene diphosphonate (MDP), was studied in rats with hypovascular HSN liver tumours. MDP was injected regionally, via the hepatic artery, alone or coadministered with DSM, with or without subsequent occlusion of either the hepatic artery or the portal vein. Tumour vascularity was measured with Co-57-labelled microspheres. Co-injection with DSM immediately significantly increased hepatic retention of marker in both tumour (T) (median 22.40 (range 16.82-59.58)% injected dose) and normal liver (N) (9.08 (4.85-12.59) %ID) the greater effect seen in T (P<0.01). After DSM degradation, very little MDP remained in N (0.61 (0.28-1.40) %ID) but there was significant retention in T (10.01 (6.73-20.28) %ID, P<0.01). Clamping the hepatic artery had minimal effect on the retention of MDP when administered alone. Regional injection of 16.5 mu m Co-57 microspheres resulted in a N:T ratio of 2.25:1. Concomitant injection of the 40 mu m DSM with Co-57 microspheres reversed this ratio to 1:2. The results indicate that DSM selectively enhances the retention of MDP to a hypovascular hepatic tumour, not by causing intra-tumour stasis, but by directing a greater arterial Row to hypovascular areas in the liver.