SU‐FF‐T‐43: Feasibility of Using Radioactive Bone Cement to Treat Vertebral Metastases

Purpose: To evaluate the feasibility of using radioactive bone cement to deliver therapeutic radiation to the vertebral body without undue risk to the spinal cord, i.e. vertebral brachytherapy. Method and Materials: CT‐scan based Monte Carlo N‐Particle radiation transport models, consisting of a three‐dimensional rectangular lattice of 0.625×0.625×1.25‐mm voxels, were created of a T‐12 human cadaveric vertebra. Trabecular and cortical bone were both represented by a spectrum of thirty complementary volume fractions of solid cortical bone and bone marrow, and all soft tissue was represented as a single material. A cylindrical volume of radioactive bone cement was simulated within the model, and two candidate radioisotopes were studied: P‐32 and Sr‐89. Thirty million particle histories were simulated (MCNPX v.2.5.0) to characterize the dose distribution within the vertebral body. Results: The dose distributions for both radioisotopes were axisymmetric about the cement implant and rapidly decreased with increasing distance from the cement. Initial activities of 0.94 mCi and 0.51 mCi for P‐32 and Sr‐89, respectively, would deliver >300 Gy to bone within 1.6 mm of the cement implant and >80 Gy to bone within 2.8 mm, while keeping the dose at 3.4 mm under 45 Gy. Conclusion: The predicted dose distributions show that a therapeutic radiation dose would be delivered to all bone within ∼3 mm of the cement without undue risk to tissue beyond 3.4 mm (such as the spinal cord), indicating preliminary feasibility of this technique. With further development, this technology may yield a clinically‐feasible procedure that would eliminate the need for 10 radiotherapy sessions, making it convenient for the patient, while potentially improving the clinical outcome by delivering a higher dose to the tumor and a lower dose to the spinal cord than conventional radiotherapy. Conflict of Interest (only if applicable): Research sponsored by Bone‐Rad Therapeutics, Inc.