Radioisotopes and vertebral augmentation: dosimetric analysis of a novel approach for the treatment of malignant compression fractures.
OBJECTIVE
Vertebral compression fractures (VCFs), a major cause of morbidity and debilitating pain, often results from secondary tumor metastases to the skeleton. Vertebral augmentation is a palliative technique developed to treat VCFs and involves the injection of polymethyl methacrylate (PMMA) to augment the fractured vertebral body. The authors investigate the feasibility of radionuclide therapy coupled with vertebral augmentation to treat both the tumor metastases and VCFs. Six therapeutic radioisotopes, uniformly mixed in a PMMA bolus, were investigated for their dosimetric properties.


METHODS
The MCNP5 Monte Carlo computer code was used to characterize the therapeutic dosimetric distribution within a cortical bone phantom for a 1 mm radial bolus of isotope-infused PMMA. Based on these data, the minimum activity required for a therapeutic treatment was calculated.


RESULTS
The dosimetry from beta emitting Y-90, P-32, and Ho-166 decreased to 10% of its maximum therapeutic dose (R10%) after traveling 1.20 mm, 1.03 mm, and 0.97 mm, respectively, through cortical bone. Low photon energy I-125 had a slightly larger calculated R10% of 1.32 mm. Although F-18 and Tc-99m exhibited a more uniform distribution (R10%=1.72 mm and 1.94 mm, respectively), the lower dosimetric gradients resulted in significantly greater therapeutic implant activities relative to the other isotopes studied in this report.


CONCLUSIONS
Radionuclide therapy coupled with vertebral augmentation is shown to be a feasible technique for the treatment of secondary skeletal metastases and its resulting side effects. Future studies will include a full clinical investigation to determine optimal treatment isotope(s).
Hirsch
Ariel E
AE
Department of Radiation Oncology, Boston University Medical Center, Boston, MA 02118, USA. ariel.hirsch@bmc.org
Medich
David C
DC
Rosenstein
Barry S
BS
Martel
Christopher B
CB
Hirsch
Joshua A
JA
D005240:Feasibility Studies; D050815:Fractures, Compression / Q000209:etiology / Q000628:therapy*; D006801:Humans; D009010:Monte Carlo Method; D010166:Palliative Care / Q000379:methods*; D019904:Polymethyl Methacrylate / Q000008:administration & dosage*; D011868:Radioisotopes / Q000627:therapeutic use*; D011874:Radiometry; D016103:Spinal Fractures / Q000209:etiology / Q000628:therapy*; D013125:Spinal Neoplasms / Q000150:complications* / Q000556:secondary; D016896:Treatment Outcome
D011868:Radioisotopes; D019904:Polymethyl Methacrylate