Effective local control of prostate cancer by intratumoral injection of ¹⁶⁶Ho-chitosan complex (DW-166HC) in rats

The aim of this study was to evaluate the therapeutic effect and morphological alterations resulting from ¹⁶⁶Ho-chitosan complex (DW-166HC) in an animal model of prostate cancer.

First, in a subcutaneous tumor model, 80 rats were randomly divided into four groups (n=20 in each group), and intratumoral injections of 0.05 ml (normal saline in group 1, ¹⁶⁵Ho-chitosan complex solution in group 2, DW-166HC solution (10 mCi) in group 3, and DW-166HC solution (20 mCi) in group 4) were performed when the tumor measured approximately 1 cm along its long axis in each group. Further, in an orthotopic tumor model, 40 rats were similarly randomly divided into four groups (n=10 in each group), and intraprostatic injections of 0.05 ml [PBS in group 1, ¹⁶⁵Ho-chitosan complex solution in group 2, DW-166HC solution (0.5 mCi) in group 3 and DW-166HC solution (1 mCi) in group 4] were performed at 1 week after implantation of the AIT cell line in the ventral prostate.

In the subcutaneous tumor model, mean tumor weights of groups 3 and 4 were significantly lower than those of groups 1 and 2 at 2 and 4 weeks post injection (p<0.05). At 2 and 4 weeks after injection in the orthotopic tumor model, the mean weights of the prostate, including tumor, in groups 3 and 4 were also significantly lower than those in groups 1 and 2 (p<0.05). No adverse injury was seen in adjacent organs at histopathologic examination.

Intratumoral injection of the beta-emitting radionuclide ¹⁶⁶Ho as a form of complex solution with chitosan appears to be a promising alternative therapeutic modality for the local control of prostate cancer.