Distribution of radioiodinated estramustine binding protein antibody in mice with DU-145 prostate cancer xenograft.

BACKGROUND Estramustine phosphate (EMP) and estramustine binding protein antibody (EMBP-AB) accumulate in the mouse prostate. The distribution of radioiodinated EMBP-AB in tumor mice was investigated to assess its therapeutic potential against prostate cancer. MATERIALS AND METHODS Mice with DU-145 prostate cancer xenografts received 243 microCi of I-125-labeled EMBP-AB (RI-EMBP-AB). The concentration of activity in different organs was measured 4 h after the injection. RESULTS The blood contained 0.45% of the injected dose per gram, the prostate 2.4%, the testes 0.95% and the tumor 0.65%. Radioactivity in these organs decreased more rapidly than in other organs. The doses of radiation absorbed by the prostate and the tumor, assuming a 1 mCi injected dose, were 1.81 and 0.92 cGy, respectively. CONCLUSION Most other organs would receive relatively high doses of radioactivity, were I-125 to be used in therapeutic doses. Therefore, RI-EMBP-AB is not beneficial in radionuclide treatment as compared to possible EMP applications.