Renal and Intestinal Excretion of 90Y and 166Ho After Transarterial Radioembolization of Liver Tumors.

OBJECTIVE. The aim of this study was to evaluate the amount of free radioactivity in renal and intestinal excretions during the first 48 hours after transarterial radioembolization (TARE) procedures on the liver. SUBJECTS AND METHODS. Urinary, intestinal, and biliary excretions of patients who underwent TARE with three different types of microspheres were collected during a postinterventional period of 48 hours (divided into two 24-hour intervals). Radioactivity measurements were performed. The detected amounts of activity were correlated to clinical and procedural characteristics, times of excretion, and microsphere types. RESULTS. Twenty-four patients were evaluated, 10 treated with 90Y-glass, 10 with 90Y-resin, and four with 166Ho-poly-L-lactic acid (PLLA) microspheres. Activity excretion occurred in all cases. The highest total excretion proportions of the injected activities were 0.011% for 90Y-glass, 0.119% for 90Y-resin, and 0.005% for 166Ho-PLLA microspheres. Intestinal excretion was markedly less than renal excretion (p < 0.001). Excretion after TARE with 90Y-resin was statistically significantly higher than with 90Y-glass or 166Ho-PLLA micro-spheres (p = 0.002). For each microsphere type, the excreted activity was independent of the activity of the injected microspheres. CONCLUSION. Renal and intestinal excretion of radioactivity after TARE is low but not negligible. The radiation risk for individuals interacting with patients can be minimized if contact with urine and bile is avoided, particularly during the first 24 hours after the procedure.

Biodistribution and excretion of radioactivity after the administration of 166Ho-chitosan complex (DW-166HC) into the prostate of rat.

PURPOSE: The objective of this study was to determine the fate of the 166Ho-chitosan complex (DW-166HC) in rats by examining its absorption, distribution and excretion after administration into the prostate. METHODS: About 100 microCi of DW-166HC [containing 0.1875 mg of Ho(NO3)3.5H2O and 0.25 mg of chitosan] was administered intraprostatically. The level of radioactivity in blood, urinary and faecal excretion, and radioactivity distribution were examined. To determine the effect of chitosan in DW-166HC, 166Ho nitrate alone [0.1875 mg of Ho(NO3)3.5H2O] was administered into the prostate of male rats, and radioactivity distribution was examined using whole-body autoradiography. RESULTS: After administration of DW-166HC into the prostate, cumulative urinary and faecal excretion over the period 0-72 h was 0.35% and 0.11%, respectively. The radioactivity at the administration site was extremely high at all time points up to 144 h (>98% of injected dose). The small amount of radioactivity which did transfer from the administration site distributed mainly to the liver, spleen, kidney cortex and bone. Compared with the DW-166HC group, the group that received 166Ho nitrate alone displayed three- to fourfold higher levels of radioactivity in the main tissues, including liver, spleen, kidney cortex and bone, at 24 h after administration (P < 0.05). CONCLUSION: The results of this study show clearly that most of the administered DW-166HC remained at the administration site. It is concluded that the chitosan complex may be used to retain 166Ho within a limited area in cancer of the prostate.

Biodistribution and kinetics of holmium-166-chitosan complex (DW-166HC) in rats and mice.

UNLABELLED: The fate of 166Ho-chitosan complex, a radiopharmaceutical drug for cancer therapy, was determined by studying its absorption, distribution and excretion in rats and mice. METHODS: Holmium-166-chitosan complex [0.75 mg of Ho(NO3)3 x 5H2O and 1 mg chitosan/ head] was administered intrahepatically to male rats. Radioactive concentrations in blood, urinary and fecal excretion and radioactive distribution in tissues were examined. To determine the effects of chitosan in 166Ho-chitosan complex, 166Ho alone [0.75 mg of Ho(NO3)3 x 5H2O/head] was intrahepatically administered to male rats, and radioactive concentrations in blood, urinary and fecal excretion and radioactive distribution were examined. In B16 melanoma-transplanted nude mice, radioactive distribution after intratumoral administration of 166Ho-chitosan complex [0.075 mg of Ho(NO3)3 x 5H2O and 0.10 mg chitosan/head] was investigated also. RESULTS: After administration of 166Ho-chitosan complex, the radioactive concentrations in blood were low, and cumulative urinary and fecal excretions over a period of 0-72 hr were 0.53% and 0.54%, respectively. The radioactive concentrations in tissues and the whole-body autoradiography images showed that most of the administered radioactivity was localized at the administration site, and only slight radioactivity was detected from the liver, spleen, lungs and bones. On the other hand, results of intrahepatic administration of 166Ho alone showed high radioactive concentrations in the blood, and the whole-body autoradiographs showed that the administered radioactivity was distributed in many organs and tissues. These results strongly suggest that 166Ho is retained at the administration site only when it forms a chelate complex with chitosan. Autoradiographs after intratumoral administration of 166Ho-chitosan complex showed that radioactivity was localized at the site of administration without distribution to the other organs and tissues. CONCLUSION: Administered 166Ho-chitosan complex is retained at the administration site after either intrahepatic or intratumoral administration to rats or tumor-transplanted nude mice.