Spinal cord compression due to spinal metastases is a medical emergency. Modern treatment approaches — minimally invasive surgical techniques and spinal stereotactic radiosurgery (SSRS) — have fundamentally shifted the paradigm from providing short-term palliation and pain relief to delivering durable tumor control with fewer morbidities than older approaches. Therefore, cancer patients who have symptoms of spinal cord compression should be referred for surgical evaluation as soon as possible.
Malignant Epidural Spinal Cord Compression
Malignant epidural spinal cord compression (MESCC) has become increasingly more common as advances in cancer therapies have led to improved outcomes for more patients. Approximately 40 percent of all people with cancer develop spinal metastases, and within that group, about 20 percent progress to symptomatic spinal cord compression. (1)
Patients presenting in the emergency setting with MESCC are often misdiagnosed. A retrospective study of 63 patients with spinal cord compression (not necessarily malignant) found that 29 percent (18) were misdiagnosed despite significant apparent neurological deficits. (2)
When cancer patients present with symptoms of spinal compression, physicians and emergency room doctors should suspect spinal metastases until proven otherwise.
A red flag on presentation is back pain. Research show that patients with MESCC experienced back pain for a median of 62 days prior to treatment, and those people presenting with radiculopathy are usually symptomatic an average of nine weeks prior to diagnosis. (2)
Clinician awareness, prompt evaluation and timely referral for surgical treatment are essential to help prevent irreversible damage to the spinal cord (3)and preserve patients’ functional independence.
Improved Surgical Strategies
Minimally invasive spine surgical techniques that use inch-long incisions have several advantages over traditional open surgical methods that require incisions of six to ten inches long. The benefits include minimal interruption or delay of cancer therapy, preserved muscle function, reduced skin damage, less pain, and faster recovery. Percutaneous cement augmentation and pedicle screw fixation can significantly improve quality of life, even for patients with limited survival. (1)
In our recently published study, we examined patient-reported outcomes in 131 patients who underwent stabilization for metastatic spinal tumor treatment. We found that stabilization significantly improved nearly all patient-reported outcome measures for patients with an indeterminate and unstable spinal instability neoplastic score (SINS). The results validated the use of SINS as a tool for determining which patients will benefit the most from surgical stabilization. (4)
Integrating Spinal Stereotactic Radiosurgery
Traditional surgical techniques used with conventional external-beam radiation therapy (cEBRT) involve invasive procedures to achieve maximum cytoreduction. Local recurrence rates with those methods have been estimated at 60 percent at six months and 96 percent at four years. (1)
With SSRS, the surgical goal has shifted to solely creating a target for the safe delivery of radiotherapy. Separation surgery is a minimally invasive epidural decompression procedure that uses posterior instrumented fusion to create a 2 mm space between the spinal cord and the tumor, without resecting the tumor or the vertebral body. (1)SSRS typically uses a single dose of 16 to 24 grays (Gy) or a hypofractionated dose of 24 to 30 Gy in two or three fractions, providing a significantly higher and more precise dose delivery compared with cEBRT, which commonly delivers a total dose of 30 Gy in ten fractions. (1)
In a retrospective review of outcomes for 186 patients undergoing separation surgery followed by SSRS, we found that the strategy was safe and effective in establishing local tumor control, regardless of tumor histology–specific radiosensitivity. Overall, the rate of local tumor progression at one year was 16.4 percent. The only significant factor affecting the rate of progression was SSRS dose, with the higher dose group showing 4 percent tumor progression compared with 22 percent in the lower dose group. (5)
We also conducted prospective research to evaluate patient-reported outcomes for 111 patients with MESCC who underwent separation surgery followed by a median postoperative SSRS dose of 2,700 centigrays. The hybrid approach resulted in significant pain reduction in all pain measures, including severity, interference with daily activities, and overall pain experience. (6) These findings confirm the benefit of separation surgery followed by SSRS and provide a strong rationale for the early referral of patients with MESCC for surgical evaluation.
Multidisciplinary Evaluation: The NOMS Decision Framework
Evaluation and treatment of spinal metastases and MESCC require multidisciplinary collaboration between medical oncologists, radiation oncologists, surgeons, interventionalists, and pain specialists.
Because treatment options are always evolving, physicians at Memorial Sloan Kettering developed a decision framework more than 15 years ago based on the experience of the spinal oncology team. The beauty of the NOMS decision framework (neurologic, oncologic, mechanical instability, and systemic) is that it has allowed MSK doctors to incorporate new treatment modalities as they have become available over time. There are four areas of evaluation:
This area examines the presence of clinical myelopathy or radiculopathy and the extent of epidural spinal cord compression (ESCC). Patients without neurologic deficits and tumors confined to bone or patients with epidural extension without spinal cord compression are classified as low-grade ESCC. Patients with spinal cord compression are classified as high-grade ESCC.
This item evaluates tumor histology and sensitivity to systemic and conventional fractionated radiation therapy. Hematologic malignancies and breast and prostate carcinomas usually show a consistent and durable response to cEBRT and are classified as radiosensitive. Solid tumors other than lung and breast — such as melanoma, sarcoma, and lung, renal, and colorectal carcinomas — do not usually respond sufficiently to cEBRT and are classified as radioresistant. Radiosensitive tumors can be treated with cEBRT regardless of the degree of cord compression; however, radioresistant tumors require SSRS.
For this evaluation, we use SINS, which assesses the level and quality of pain, the extent of osteolysis, deformity, and vertebral body and posterior element involvement. Patients with severe spinal instability require stabilization procedures, such as vertebral cement augmentation, or percutaneous or open instrumented fixation.
This area considers the extent of metastatic tumor burden and comorbidities to evaluate whether the patient can tolerate surgery, radiation, and chemotherapy.
At MSK, the Spine Tumor Team evaluates and treats more than 1,500 spine tumors a year. Last year, we performed more than 4,000 procedures. Our objective is to create the most effective individualized treatment plan for each patient to improve neurologic function and mobility, stabilize the spine, control local tumor progression, and improve quality of life.
Our team continues to research the delivery and effectiveness of radiosurgery. We developed a novel six-point grading system that takes recent advances in surgical approaches and radiation oncology into account. It can be used to inform treatment decisions and outcomes in clinical studies. (7)We are also designing and overseeing longitudinal studies and prospective clinical trials designed to determine the optimal treatment for patients with spinal tumors. For example, we are currently conducting a phase I dose escalation study of single-dose, image-guided stereotactic radiosurgery to assess toxicities, local tumor control failure, and overall survival at two years in patients with spinal metastases that have already been treated with radiation therapy.
Neurosurgeon Mark Bilsky, Director of Memorial Sloan Kettering’s Spine Tumor Center, talks about advances in the treatment of spine tumors with radiation therapy, surgery, and other procedures.