Estimation of exposure of metastatic foci and critical bone structures in the performance of radionuclide therapy with 153Sm-oxabifor

Absorbed radiation doses to metastatic foci were estimated in 16 patients with bone metastases from different tumors, who received 153Sm-oxabifor injection (1.0 mCi/kg of body mass) for palliative treatment. The uptake rate for the radiopharmaceutical was estimated by relative accumulation of the radionuclide in the uptake foci. The conjugate view method was used to determine the activity of 153Sm. The gamma-camera sensitivity coefficients were obtained based on measurements of the activity of 153Sm standard sources. Absorbed doses to critical organs (red bone marrow and endosteal layer) were calculated using the adjusted MIRD methods, whereas doses to metastases were obtained with the homogenous structure model. The absorbed doses to metastatic foci were found to range from 2 to 91 Gy and the spread in the radiation doses to the critical organs was: [0.6÷1.7] Gy for red bone marrow, [2.0÷5.6] Gy for endosteal layer.