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A Treatment Planning Method for Sequentially Combining Radiopharmaceutical Therapy and External Radiation Therapy

2010; Elsevier BV; Volume: 80; Issue: 4 Linguagem: Inglês

10.1016/j.ijrobp.2010.08.022

1879-355X

Robert F. Hobbs, Todd McNutt, Sébastien Baechler, Bin He, Caroline Esaias, Eric C. Frey, David M. Loeb, Richard L. Wahl, Ori Shokek, George Sgouros,

Management of metastatic bone disease

Purpose Effective cancer treatment generally requires combination therapy. The combination of external beam therapy (XRT) with radiopharmaceutical therapy (RPT) requires accurate three-dimensional dose calculations to avoid toxicity and evaluate efficacy. We have developed and tested a treatment planning method, using the patient-specific three-dimensional dosimetry package 3D-RD, for sequentially combined RPT/XRT therapy designed to limit toxicity to organs at risk. Methods and Materials The biologic effective dose (BED) was used to translate voxelized RPT absorbed dose (DRPT) values into a normalized total dose (or equivalent 2-Gy-fraction XRT absorbed dose), NTDRPT map. The BED was calculated numerically using an algorithmic approach, which enabled a more accurate calculation of BED and NTDRPT. A treatment plan from the combined Samarium-153 and external beam was designed that would deliver a tumoricidal dose while delivering no more than 50 Gy of NTDsum to the spinal cord of a patient with a paraspinal tumor. Results The average voxel NTDRPT to tumor from RPT was 22.6 Gy (range, 1–85 Gy); the maximum spinal cord voxel NTDRPT from RPT was 6.8 Gy. The combined therapy NTDsum to tumor was 71.5 Gy (range, 40–135 Gy) for a maximum voxel spinal cord NTDsum equal to the maximum tolerated dose of 50 Gy. Conclusions A method that enables real-time treatment planning of combined RPT-XRT has been developed. By implementing a more generalized conversion between the dose values from the two modalities and an activity-based treatment of partial volume effects, the reliability of combination therapy treatment planning has been expanded. Effective cancer treatment generally requires combination therapy. The combination of external beam therapy (XRT) with radiopharmaceutical therapy (RPT) requires accurate three-dimensional dose calculations to avoid toxicity and evaluate efficacy. We have developed and tested a treatment planning method, using the patient-specific three-dimensional dosimetry package 3D-RD, for sequentially combined RPT/XRT therapy designed to limit toxicity to organs at risk. The biologic effective dose (BED) was used to translate voxelized RPT absorbed dose (DRPT) values into a normalized total dose (or equivalent 2-Gy-fraction XRT absorbed dose), NTDRPT map. The BED was calculated numerically using an algorithmic approach, which enabled a more accurate calculation of BED and NTDRPT. A treatment plan from the combined Samarium-153 and external beam was designed that would deliver a tumoricidal dose while delivering no more than 50 Gy of NTDsum to the spinal cord of a patient with a paraspinal tumor. The average voxel NTDRPT to tumor from RPT was 22.6 Gy (range, 1–85 Gy); the maximum spinal cord voxel NTDRPT from RPT was 6.8 Gy. The combined therapy NTDsum to tumor was 71.5 Gy (range, 40–135 Gy) for a maximum voxel spinal cord NTDsum equal to the maximum tolerated dose of 50 Gy. A method that enables real-time treatment planning of combined RPT-XRT has been developed. By implementing a more generalized conversion between the dose values from the two modalities and an activity-based treatment of partial volume effects, the reliability of combination therapy treatment planning has been expanded.