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An amendment to this paper has been published and can be accessed via the original article.
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PURPOSE: To evaluate the safety, feasibility, and preliminary efficacy of yttrium-90 (90Y) radioembolization (RE) as a minimally invasive treatment in a canine model with presumed spontaneous brain cancers. MATERIALS: Three healthy research dogs (R1-R3) and five patient dogs with spontaneous intra-axial brain masses (P1-P5) underwent cerebral artery RE with 90Y glass microspheres (TheraSphere). 90Y-RE was performed on research dogs from the unilateral internal carotid artery (ICA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) while animals with brain masses were treated from the ICA. Post-treatment 90Y PET/CT was performed along with serial neurological exams by a veterinary neurologist. One month after treatment, research dogs were euthanized and the brains were extracted and sent for microdosimetric and histopathologic analyses. Patient dogs received post-treatment MRI at 1-, 3-, and 6-month intervals with long-term veterinary follow-up. RESULTS: The average absorbed dose to treated tissue in R1-R3 was 14.0, 30.9, and 73.2 Gy, respectively, with maximum doses exceeding 1000 Gy. One month after treatment, research dog pathologic analysis revealed no evidence of cortical atrophy and rare foci consistent with chronic infarcts, e.g., < 2-mm diameter. Absorbed doses to masses in P1-P5 were 45.5, 57.6, 58.1, 45.4, and 64.1 Gy while the dose to uninvolved brain tissue was 15.4, 27.6, 19.2, 16.7, and 33.3 G, respectively. Among both research and patient animals, 6 developed acute neurologic deficits following treatment. However, in all surviving dogs, the deficits were transient resolving between 7 and 33 days post-therapy. At 1 month post-therapy, patient animals showed a 24-94% reduction in mass volume with partial response in P1, P3, and P4 at 6 months post-treatment. While P2 initially showed a response, by 5 months, the mass had advanced beyond pre-treatment size, and the dog was euthanized. CONCLUSION: This proof of concept demonstrates the technical feasibility and safety of 90Y-RE in dogs, while preliminary, initial data on the efficacy of 90Y-RE as a potential treatment for brain cancer is encouraging.
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CASE DESCRIPTION A 9-year-old spayed female Rottweiler with hind limb ataxia was examined because of anorexia and an acute onset of hind limb paresis. CLINICAL FINDINGS Neurologic evaluation revealed hind limb ataxia and symmetric paraparesis with bilaterally abnormal hind limb postural reactions including hopping, hemiwalking, hemistanding, and delayed proprioception, which were suggestive of a lesion somewhere in the T3-L3 segment of the spinal cord. Thoracolumbar radiography revealed an abnormal radiopacity suggestive of a mass at T11. Two 3.5-cm-long osseous core biopsy specimens of the mass were obtained by MRI guidance. Histologic appearance of the specimens was consistent with osteosarcoma. TREATMENT AND OUTCOME The owners of the dog declined further treatment owing to a poor prognosis. The dog was euthanized within 12 months after diagnosis because of a declining quality of life. CLINICAL RELEVANCE The acquisition of biopsy specimens by MRI guidance is an emerging technique in veterinary medicine. As evidenced by the dog of this report, MRI-guided biopsy can be used to safely obtain diagnostic biopsy specimens from tissues at anatomic locations that are difficult to access. This technique can potentially be used to facilitate early diagnosis and treatment of disease, which could improve patient outcome. The MRI guidance technique described may also be useful for local administration of chemotherapeutics or radiofrequency ablation or cryoablation of various neoplasms of the vertebral column.
