Significant advances have been made in the treatment of spinal metastases in recent years. Options have evolved from simple decompression surgery or conventional external bean radiotherapy (cEBRT) to complex multi-disciplinary treatments incorporating stereotactic radio surgery (SRS) and minimally invasive surgical techniques (MIS). This is important as 60% of all patients with cancer will develop spinal metastases and 5-10% will develop spinal cord compression. The aims of therapy for these patients should involve preserving neurological function along with spinal stability, pain control and local tumorcontrol.
Common presenting symptoms of spinal metastatic disease include back pain and neurological deficit. The assessment of pain must address its nature, mechanical versus the night time biological pain, radiation and improvement on steroids. Neurologic deficits should be self evident on history and examination with weakness, and sensory disturbance or bladder and bowel impairment. A surprising number of patients will however be asymptomatic and have spinal disease picked up on staging imaging such as PET. Imaging studies may include x-ray or CT as first line but MRI is gold standard and whole spine imaging is mandatory given the frequency of multifocal disease. For patients with known malignancy a physician must always have a low threshold for spine imaging.
The NOMS framework developed at Memorial Sloan-Kettering Cancer Center aims to provide a system that integrates four fundamental assessments: Neurologic, Oncologic, Mechanical instability and Systemic disease.
Neurologic assessment involves evaluation of the degree of epidural spinal cord compression (ESCC) and clinical assessments of myelopathy or functional radiculopathy. ESCC is graded on a score validated by the Spine Oncology Study Group.
Oncological assessment is centered around the degree of response to potential treatment such as cEBRT, SRS, surgery, chemotherapy, hormonal, targeted or immunotherapeutic agents. Currently radiation is the mainstay of spinal metastasis and therefore the primary consideration. On the basis of expected response to cEBRT tumors may be considered radiosensitive (such as lymphoma, breast or prostate) or radio resistant (such as sarcoma, melanoma, lung (NSCLS) and renal cell). The game has changed with the advent of SRS for these tumors with durable local control in patients with oligometastatic tumors treated with 24Gy regardless of tumour histology. The efficacy of high dose SRS for local control has reduced the need for extenisive surgical resections with resultant morbidity.
While radiation is effective it has no impact on spinal stability in the presence of pathological fractures. Mechanical instability presents usually with movement related pain at the level involved with possible radicular component. This pain should be easily distinguished from biologic pain which presents in evening and morning and readily responds to steroids. The degree of instability can be assessed using the Spinal Instability Neoplastic Score (SINS). The most important factor is however pain and this can be in the form of mechanical back pain from movement at an unstable segment or radicular pain from compression of the exiting nerve roots. These problems respond well to a range of surgical interventions. In the absence of spinal cord compression stabilization may be achieved with kyphoplasty or minimally invasive percutanous surgery. In cases where there is cord compression open decompressing and fusion surgery is required. There is now less emphasis placed on large invasive surgeries to resect these tumors given the success of SRS in achieving local control.
Systemic disease includes extent of oncological disease as well as medical co-morbities to evaluate the patient’s ability to undergo proposed treatments. It must be remembered that in nearly all cases interventions for spinal metastasis are palliative in nature and the goals must be clear. However even in advanced disease there may be significant benefit in terms of pain control and preservation of neurological function with judicious intervention.
In conclusion spinal tumors represent a complex problem and the treatment options must be tailored to individual patients. Treating physicians must maintain a high index of suspicion and a low threshold for imaging in all cancer patients.