Commentary (Byrne): Early Detection and Treatment of Spinal Cord Compression

As outlined by Dr. Ruckdeschel, the evaluation and manage ment of metastatic spinal metastases and associated epidural spinal cord compression have been simplified by the advent of magnetic resonance imaging (MRI), which is much more sensitive and specific than plain x-rays and radionuclide bone scanning. Furthermore, because most patients can now undergo MRI rather than invasive myelography, the threshold for diagnosing epidural metastatic disease has been lowered. Accordingly, it has become the test of choice for evaluating most patients with suspected spinal metastases. In addition, Dr. Ruckdeschel appropriately reminds us that cancer patients with back pain and/or radicular pain can have a normal neurologic examination and normal plain x-rays and still have metastatic epidural spinal cord compression. Therefore, the development of such pain-especially if it is new-in the cancer patient should arouse the suspicion that metastatic spinal cord compression could be present even if the neurologic examination is normal. In recent years, several reports have had an impact on the evaluation and management of spinal metastases and metastatic epidural spinal cord compression. Selected articles are briefly reviewed below. Prognostic Factors
A recent prospective study by Rades et al[1] reported that the time to the development of motor deficits before radiation therapy (surgical patients were excluded) is helpful in predicting ambulatory outcome. The authors divided 98 patients into three cohorts, which were segregated according to how long it took the motor deficit to develop: group A, 1 to 7 days; group B, 8 to 14 days; and group C, more than 14 days. The starting point for determining the preradiotherapy time to motor deficit development was the onset of any symptoms. Preradiotherapy ambulatory rates were similar: 48%, 55%, and 56%, respectively. The investigators found that postradiotherapy ambulatory rates were 35% in group A, 55% in group B, and 86% in group C. They concluded that the time over which a motor deficit developed is an important prognostic factor in predicting functional outcome and suggested that this parameter be included in the analysis of future studies designed to evaluate the management of metastatic epidural spinal cord compression. Management
Since the late 1970s, the treatment of metastatic epidural spinal cord compression in the majority of cases has been radiotherapy and corticosteroids, because it was found that laminectomy followed by radiotherapy was not superior to radiotherapy alone.[2] Since the 1980s, vertebral body resection followed by stabilization of the spine with instrumentation has been performed in selected patients. In 1998, Loblaw and Laperriere[3] wrote an evidence-based guideline regarding the emergency management of metastatic epidural spinal cord compression. They found inconclusive evidence to make a strong recommendation regarding selection of patients for surgery (ie, vertebral body resection or laminectomy with or without stabilization). However, based on expert opinion, they did recommend surgery for patients with spinal instability and bony compression of the spinal canal. In 2003, Hirabayashi et al[4] reported their retrospective experience with 81 patients who underwent surgical treatment of metastatic tumors between 1985 and 2001. Most patients underwent a posterior approach and, in more recent years, spinal instrumentation to prevent progressive kyphosis. Of the 81 patients, 31 (38%) were ambulatory preoperatively, whereas 57 (70%) were ambulatory postoperatively. The overall median survival was 10.6 months. The authors concluded that survival time is more strongly correlated with the biology of the malignancy than the preoperative ambulatory status. The finding that preoperative ambulatory status did not strongly correlate with survival is at variance with other studies. One potential explanation may be that the rate of motor deficit was not reported. Other limitations to this study included the following factors: It was retrospective, 26 of the original 107 patients were unavailable for follow-up, and the histologies of the primaries were atypical with only 4 patients having breast cancer, whereas 6 had thyroid cancer. As mentioned by Dr. Ruckdeschel, a recent preliminary report of a prospective randomized study concluded that radical decompressive surgical resection of metastatic tumor and spinal stabilization followed by irradiation resulted in a superior outcome to radiation therapy alone in the management of metastatic epidural spinal cord compression.[5] Because this study by Patchell et al was reported only in abstract form as of the time of this writing, many of its details are unknown. Furthermore, a number of questions are raised by the report, including the issue of patient selection. For example, does the study confirm the impression of Loblaw and Laperriere[3] that bony compression of the spinal canal or spinal instability is better managed by surgery followed by radiotherapy rather than radiotherapy alone? Alternatively, is the benefit of the combined treatment seen independent of whether there is spinal instability and/or bony compression? Is the benefit seen in all primary tumor types? Does the time over which motor deficits develop influence the outcome, as reported by Rades et al?[1] Other treatments that have been recently reported in the management of patients with vertebral metastases include vertebroplasty and kyphoplasty. Fourney et al[6] selected patients with vertebral metastases but no neural compression to undergo vertebroplasty or kyphoplasty. They reported improved pain control at 1 month; however, the improvement in ambulatory status was not statistically significant. The risks and benefits of these therapies await randomized trials. Conclusions
As Dr. Ruckdeschel notes, with the advent of MRI, we are in a far better position to make an early diagnosis of spinal metastases before neurologic deficits develop. Recent advances in our understanding of the prognostic factors and treatments are expected to broaden the management options and improve the outcomes of patients with spinal metastases and metastatic epidural spinal cord compression.

Disclosures:

The author has no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.

References:

1. Rades D, Heidenreich F, Karstens JH: Final results of a prospective study of the prognostic value of the time to develop motor deficits before irradiation in metastatic spinal cord compression. Int J Radiat Oncol Biol Phys 53:975- 979, 2002.
2. Gilbert RW, Kim JH, Posner JB: Epidural spinal cord compression from metastatic tumor: Diagnosis and treatment. Ann Neurol 3:40-51, 1978.
3. Loblaw DA, Laperriere N: Emergency treatment of malignant extradural spinal cord compression: An evidence-based guideline. J Clin Oncol 16:1613-1624, 1998.
4. Hirabayashi H, Ebara S, Kinoshita T, et al: Clinical outcome and survival after palliative surgery for spinal metastases. Cancer 97:476- 484, 2003.
5. Patchell R, Tibbs PA, Regine WF, et al: A randomized trial of direct decompressive surgical resection in the treatment of spinal cord compression caused by metastasis (abstract 2). Proc Am Soc Clin Oncol 22:1, 2003.
6. Fourney DR, Schomer DF, Nader R, et al: Percutaneous vertebroplasty and kyphoplasty for painful vertebral fractures in cancer patients. J Neurosurg (Spine 1) 98:21-30, 2003.