SAMARIUM-153-EDTMP BIODISTRIBUTION AND DOSIMETRY ESTIMATION

Fifty-two patients were treated with single doses of Sm-153-EDTMP in a Phase I escalating dose protocol for palliation of bone pain from met astatic prostate carcinoma. Samarium-153 (T1/2 46.3 hr), maximum beta- particle energies 810 keV (20%), 71 0 keV (30%), 640 keV (500/.), gam ma photon 103 keV (28%), was complexed to the tetraphosphonate chelate , EDTMP. Five groups of patients were treated at doses of 1.0, 1.5, 2. 0, 2.5, and 3.0 mCi/kg to evaluate toxicity from treatment. Patients w ere screened prior to treatment and followed after treatment with Tc-9 9m-MDP bone scans. Biodistribution data on this group of patients were acquired and showed rapid uptake of Sm-153-EDTMP into bone with compl ete clearance of nonskeletal radiotoxicity by 6-8 hr. Also included ar e complete sets of dosimetry estimations on an additional seven patien ts who received 0.5 mCi/kg Sm-153-EDTMP Ca++ as part of a multiple dos e therapy trial. Estimated radiation absorbed doses to bone surfaces a veraged 25,000 mrad/mCi (6686 Gy/MBq), and urinary bladder doses avera ged 3600 mrad/mCi (964 Gy/MBq).