Preparation and preliminary in vivo evaluation of 166 Ho-labeled microspheres for possible use in radioembolic therapy of liver cancer

Hepatocellular carcinoma (HCC) or liver cancer is an increasingly prevalent and highly morbid disease with critical significance in the Asian and African subcontinents. Among the various therapies currently used in the clinic to combat the global menace of HCC, radioembolization with suitable therapeutic isotopes is an effective targeted approach. In the Indian context, the significant cost and logistical disadvantage of imported radioembolic formulations for HCC therapy make it essential to develop more feasible indigenous alternatives—using locally available radioisotopes and microspheric carriers—that can serve the nuclear medicine community. With this aim Ho-166 was produced with good specific activity (>13 GBq mg−1) and purity (>99%) by reactor irradiation. Various commercially available microspheres were labeled with this therapeutic radioisotope, characterized for yield and stability of the radiolabeling, and tested for their in vivo retention and stability in Wistar rat model by viable surgery. Under the optimized reaction conditions, 166Ho-labeled microspheres were prepared with high yield (>94%-99%) and in vitro stability (>95%) in saline and serum. Retention studies in animal model showed that 166Ho-labeled microspheres remained stable in vivo and showed excellent retention in the site of interest (~95% at 72-hour p.i.). The study indicates good potential and warrants further investigation for application of these indigenous radiolabeled microspheres for HCC therapy. The successful application of this technology in the clinic would lead to logistically advantageous and cost-effective indigenous alternatives to expensive imported therapeutic solutions.