Radiation-induced fracture.

The advent of any new medical treatment is accompanied by a wave of enthusiasm, followed by the attendant realization that no new therapy is without risks. Such is the case with stereotactic body radiotherapy (also referred to as spine stereotactic radiosurgery [SRS]), which has been increasingly used in the treatment of metastatic spinal tumors. Stereotactic radiosurgery applies a concentrated dose of radiation to the tumor itself and away from the spinal cord, which would permit the possibility of local cure of the neoplasm, with less risk to the spinal cord compared with standard radiation therapy. Several large studies have been published assessing the safety and efficacy of this technique.4,5,7,8 In addition to the potential for bone and spinal cord damage from SRS, there is also the risk of vertebral compression fracture (VCF), estimated to be 11%–39%.1–3,6 Patients who received the highest biologically effective dose (20–24 Gy in one setting) were at greatest risk for developing VCF,3 and the etiology was hypothesized to be due to radiation-induced effects within the tumor and bone that caused structural weakening of the vertebral body. Open surgery, further radiation therapy, or chemotherapy would then be options for the treatment of this clinical problem. However, as demonstrated by Al-Omair et al.,1 radiation necrosis and not tumor progression may be the cause of VCF following SRS. The authors performed a biopsy in 2 patients who demonstrated VCF several years after SRS. Magnetic resonance imaging findings were consistent with tumor progression, but the histopathological findings were consistent with necrosis or fibrosis. Both patients underwent kyphoplasty and were spared further invasive therapy. These important findings present a dilemma for the physician faced with this clinical problem, and there are currently no management guidelines to direct treatment. As the use of SRS becomes more widespread, there are likely to be more of these patients. Should all patients who have VCF after SRS undergo biopsy? The authors recommend biopsy “when it is unclear based on imaging alone if true progression has occurred,” but this is on the basis of a single report describing 2 patients. Magnetic resonance imaging or PET scanning does not always allow these 2 pathological processes, radiation necrosis or tumor progression, to be distinguished, thus leaving the diagnostic decision in the hands of the practicing clinician. If radiation necrosis is diagnosed, what is the optimal treatment? As this problem becomes more prevalent, it is likely that indications for biopsy will emerge. In the meantime, this paper has spotlighted the discrepancy between radiology and pathology. The practicing spine surgeon will now have to remember that fibrotic or necrotic changes in the bone may mimic tumor progression and perhaps consider recommending biopsy at this diagnostic branch point. The strategy combining biopsy with concurrent kyphoplasty is attractive; however, is this the best treatment? It is obvious that more studies will need to be carried out to determine the extent of the problem and guide therapy, but this manuscript offers the necessary initial data in this (currently) little-known clinical dilemma. (http://thejns.org/doi/abs/10.3171/2013.1.SPINE121161)