Abstract
In evaluating the outcomes of stereotatic radiosurgery (SRS) in the treatment of spinal metastases, authors have looked primarily at endpoints of pain relief and tumor growth suppression. The question of structural stability has been raised, but the pattern of bone remineralization has not been investigated in detail. With traditional radiation, both tumor control and pain relief are modest, and resulting bone remineralization can reach 80% with responsive tumors. SRS offers higher rates of both tumor growth control and pain relief (88%), even for radioresistant tumors, but the protection from vertebral fracture is not improved when there is more than 40% of the vertebra involved. We report a case of a partially collapsed C2 vertebral body affected by multiple myeloma, which was surgically stabilized and treated with CyberKnife SRS. Upon a 12-month follow-up period including CT imaging, remineralization of the vertebral body was observed starting at three months post-SRS that significantly progressed during the 12-month follow-up period. Final radiographic evaluation showed almost complete restoration of the structure of the vertebral body and the associated bone densities with significantly increased stability. This pattern of remineralization is contrasted with reported results of traditional radiation therapy, and its implications for stabilization are noted.
Highlights
There are over 700,000 new cases of cancer in the U.S every year, and 35% will experience metastases to the spine [1] that will cause pain and may threaten cord function by either direct compression of the cord or by indirect bony collapse with compression
They found no explanation of this pattern, in either tumor type or amount of radiation given, and concluded that radiotherapy does not in every case lead to the desired result of remineralization to prevent fracture of the vertebral body
For patients in the 10 fraction group pain control and remineralization were better, especially for breast and prostate cancer reaching 60-80% improvement in remineralization. These results offered evidence that the responses of both pain relief and remineralization was proportionately related to the Biological Equivalent Dose (BED)
Summary
There are over 700,000 new cases of cancer in the U.S every year, and 35% will experience metastases to the spine [1] that will cause pain and may threaten cord function by either direct compression of the cord or by indirect bony collapse with compression. In the cases of a metastasis without cord compression, radiation is often chosen for the pain relief and tumor control. There have been several reports on the pattern of bone response to traditional radiation treatments in cancer patients (Table 1). The remineralization progressed from the periphery to the center of the metastatic lesion They found no explanation of this pattern, in either tumor type or amount of radiation given, and concluded that radiotherapy does not in every case lead to the desired result of remineralization to prevent fracture of the vertebral body.
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