Controlling spine metastases with tumour ‘separation surgery’ and high-dose stereotactic radiosurgery

Safe and effective – Researchers have found that tumour “separation surgery” followed by high-dose hypofractionated stereotactic radiosurgery (SRS) or high-dose single-fraction SRS is safe and effective in controlling spinal metastases regardless of the radiosensitivity of the particular tumour type that has invaded the spine. This finding is fleshed out in the article “Local disease control for spinal metastases following ‘separation surgery’ and adjuvant hypofractionated or high-dose single-fraction stereotactic radiosurgery: outcome analysis in 186 patients. Clinical article,” by Ilya Laufer, M.D., and colleagues, published today online in the Journal of Neurosurgery: Spine (http://thejns.org/doi/full/10.3171/2012.11.SPINE12111).

The authors reviewed and analyzed data in the charts of 186 patients who presented with epidural spinal cord compression due to spinal metastases. All of these patients underwent tumour separation surgery to decompress the spinal cord and stabilize the spine sometime between 2002 and 2011. During this procedure the tumour was dissected away from the spinal cord—or separated—providing a space between the spinal dura and any remaining tumour. Unlike in traditional spinal tumour surgery, extensive tumour resection was not pursued to reduce surgical morbidity. The spine was also stabilized with screws and rods.

Within 2 to 4 weeks after surgery, stereotactic radiosurgery (SRS) was performed to deliver radiation to the remaining metastatic tumour without damaging the spinal cord. In 40 patients (21.5%) radiation was delivered in a single 24-Gray (Gy) dose to the tumour (high-dose single-fraction SRS). In 37 patients (19.9%) a median total dose of 27 Gy (range 24 to 30 Gy) was delivered in three fractions (high-dose hypofractionated SRS), and in 109 patients (58.6%) a median total dose of 30 Gy (range 18 to 36 Gy) was delivered in five or six fractions (low-dose hypofractionated SRS).

In their review and analysis, the authors identified the following:

• Better local tumour control in patients who underwent high-dose hypofractionated SRS than in those who underwent low-dose hypofractionated SRS.
  • The 1-year cumulative local progression rates were 4.1% in the high-dose group and 22.6% in the latter group.
  • The difference in tumour progression–free survival between these two groups was statistically significant.
• In the group of patients who underwent single-fraction SRS, the 1-year cumulative local progression rates was 9.0%.
  • There was no statistically significant difference in tumour progression–free survival between this group and the high-dose hypofractionated SRS group.
• Other variables were examined to determine their effect on local tumour control, specifically individual patient characteristics, radiosensitivity of the metastatic tumour to conventional radiation, response to preoperative radiotherapy, grade of spinal cord compression, and extent of spinal cord decompression.
  • None of these variables significantly correlated with progression-free survival.
  • This lack of correlation confirms that the “tumour response to high-dose radiation is independent of these characteristics.”

Unlike conventional external beam radiation therapy, SRS delivers a far more focused beam of radiation to the tumour. This allows physicians to deliver large doses of radiation to diseased portions of the body and still protect surrounding healthy tissue from radiation’s effects. The authors point out that radiosensitive tumours can be treated successfully with lower doses of radiation delivered by conventional external beam radiation therapy; radioresistant tumours, on the other hand, require large doses of radiation, which are best delivered by SRS. By first performing “separation surgery,” creating a space between the spine and the remaining tumour, the surgeons protect the spinal cord from the high levels of radiation needed to treat radioresistant tumours.

The authors begin their paper by stating the rationale behind treatment of metastatic spine tumours. Care “is palliative with the goal of improving or maintaining neurological function, achieving spine stability, relieving pain, and providing durable tumour control.” The object is to make the patient as comfortable and neurologically functional as long as possible despite the presence of systemic disease. In this situation sometimes less surgery is better.

According to coauthor Dr. Mark Bilsky, “The strategy of separation surgery followed by high-dose hypofractionated or single-fraction radiation has revolutionized our ability to provide meaningful palliation for this very complicated patient population with metastatic spine tumours. This limited surgery consisting of spinal cord decompression and posterior segmental fixation is well tolerated and can be performed with limited morbidity. Instead of attempting gross total resection followed by conventional external beam radiation, separation surgery followed by SRS provides excellent durable tumour control of residual vertebral body tumours and even large paraspinal tumours, while minimizing the extent of surgical intervention. The integration and wide availability of SRS as a postoperative adjuvant following separation surgery will help shift treatment paradigms for metastatic spine tumours to ultimately provide better palliation for these patients.”

Laufer I, Iorgulescu JB, Chapman T, Lis E, Shi W, Zhang Z, Cox BW, Yamada Y, Bilsky MH. Local disease control for spinal metastases following “separation surgery” and adjuvant hypofractionated or high-dose single-fraction stereotactic radiosurgery: outcome analysis in 186 patients. Clinical article. Journal of Neurosurgery: Spine, published online January 22, 2013, ahead of print; DOI: 10.3171/2012.11.SPINE12111.

Disclosure: Dr. Laufer is a consultant for SpineWave.

This article is accompanied by an editorial: Fisher C, Batke J. Editorial. Separation surgery. Journal of Neurosurgery: Spine, published online January 22, 2013, ahead of print; DOI: 10.3171/2012.10.SPINE12734. .

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