Metastatic Spine Tumors / Spinal Metastasis
What are Metastatic Spine Tumors?
Metastasis (secondary tumour deposits at a site distant to the primary tumour) to the skeletal system is a common occurrence, particularly in the spine. Spinal metastasis may manifest from a variety of primary cancers, with lung, breast, prostate, and renal cell being most common. Within the skeletal system, metastatic disease favors the spine. Spinal metastasis occurs at any time during the progression of the primary disease. Metastatic involvement of vertebral bodies may result in compression of the spinal cord, cauda equina, or nerve roots in up to 5% of patients with cancer.
Jaffe estimated that more than 70% of patients who die from cancer have skeletal metastases that often involve the spine. The spine is the most common site for metastases within the skeletal system. Management requires recognizing and characterizing a lesion, understanding the status of a patient's disease, and treating with radiation, chemotherapy, or surgical intervention.
How is a Metastatic Spine Tumor diagnosed?
Metastatic tumors of the vertebral bodies may present with back pain or neurological deficits. Back pain in patients with known metastasis must be evaluated for spinal metastasis. Such patients should be referred for appropriate imaging for definitive diagnosis.
Once a metastatic spinal tumor is suspected, imaging techniques should be used to determine the location, the extent of neural tissue compression, the degree of damage to the vertebral body, and corresponding spinal stability. Plain films may assess vertebral body alignment and stability, as well as degree of vertebral body destruction. Plain films are poor in detecting vertebral body involvement and are more effective in later stages of metastatic disease.
Technetium-99 bone scintigraphy can be used to detect bone metastases earlier but may also create false-positive results in the cases of metabolic bone diseases or trauma and false-negative results in the cases of plasmacytoma and melanoma metastases.
Computed tomography (CT) scans are optimal for determining the extent of bone lesions and bony neural element compromise. Computed tomography scans are useful for surgery planning, information regarding the anatomy of the vertebral bodies, degree of bony destruction, and involvement of adjacent levels.
Magnetic resonance imaging (MRI) is ideal for diagnosis of metastatic spinal tumors. It offers the best visualization of the spinal column and can also be used to detect early involvement of the spinal column due to its sensitivity to bone marrow changes.
Angiography is used for vascular tumors of the spinal column, such as melanoma, hypernephroma, and thyroid carcinoma.
How is a Metastatic Spine Tumor treated?
Most patients with vertebral tumor undergo a form of radiotherapy; radiotherapy has constituted the most common initial therapeutic modality.
Because pain is a common symptom among patients with spinal metastasis, initial efforts are usually aimed at treating the source of pain to improve quality of life and patient comfort. Pain generated by epidural radicular (nerve root) compression from metastasis can often be treated with radiotherapy. However, mechanical or axial pain resulting from structural failure secondary to tumor involvement may require surgical stabilization. In these cases, radiotherapy will not prove useful in pain management.
Patients with severe neurological deficits prior to radiation treatment may not see any improvement in their condition. Patients who experience neurologic deterioration during the course of treatment have a poor prognosis for recovery of function.
Surgeons should appreciate the increased risk for peri-operative complications associated with radiotherapy. Radiation has been associated with poor healing time and impaired wound repair. Generally, radiotherapy is delayed for 2 to 4 weeks postoperatively to allow for wound healing. Rates of wound infection and wound breakdown are significantly higher in radiotherapy patients.
Complete resection and eradication of the tumor is rarely possible; the main focus of surgical treatment in the case of a patient with a spinal metastasis is pain management and possible recovery of lost neurological function.
Therefore surgery for metastatic disease of the spine is indicated for correction of deformity, preservation of neurologic function, and control of intractable pain. As surgical techniques and adjuvant therapy regimens are refined, surgical goals are becoming more attainable and outcomes are improving.