Spinal metastases occur in 4% of patients with metastatic breast cancer. The overwhelming majority of cases are caused when a bone metastasis in a vertebrae presses on the spinal cord causing spinal cord compression. While spinal cord compression is caused by bone metastases, because it can damage the spinal cord, much of the medical literature groups it with CNS metastases. Spinal cord compression damages the spinal cord by disrupting the nerve signals. It can cause paralysis of the legs and/or the arms if not treated right away. The thoracic spine (middle of the back) is the most common site for a spinal cord compression though it can also occur in the upper or lower part of the back. Intramedullary metastases are actual spinal cord metastases, a condition that is extremely rare in women with breast cancer.
- Back pain usually occurs six weeks before any other symptoms. Pain worsens when lying down, coughing, or sneezing.
- Limb weakness
- Repetitive muscle contractions
- Change in bladder or bowel function
- Sensory changes, like numbness, tingling, and intermittent "electrical" sensations
Back pain with an unknown cause and without any other symptoms may be first evaluated by an x-ray of the spine to be followed by an MRI with gadolinium if any abnormality is found. Sometimes a high resolution CT scan is necessary to distinguish a metastasis from a non-cancerous mass. Prompt diagnosis is extremely important because permanent spinal cord damage can occur without prompt treatment. If paralysis is not treated within 24 hours, it is not usually reversible.
Once the diagnosis of spinal cord compression is made, steroids should be started immediately. Higher doses of dexamethasone (Decadron) before radiation will improve the chance of being able to walk if spinal cord compression has already occurred. External beam radiation (like a long x-ray) to the region of the metastasis is the most common form of treatment. It both reduces the pain for 90% of patients, and can prevent spinal cord compression, fractures, and recurrences. For isolated, operable spinal cord metastasis, or when there is a physical compression like a broken bone that needs to be removed, surgery followed by radiation is the best treatment. Studies show that between 60% and 100% of patients who could walk before radiation maintain that ability. Unfortunately, of those who could not walk before radiotherapy, only one third regained that ability. Surgery is used before external beam radiation when there is a physical compression like a broken bone that needs to be removed.
Use of stereotactic radiosurgery (targeted high-dose radiation) is increasing. It is thought that because it provides a more targeted and higher dose of radiation, it might do a better job in preventing recurrences. There is recent evidence that surgery combined with stereotactic radiosurgery is more effective than radiosurgery alone, for those who do not have a lot of other metastases. However, since treatment takes about an hour and a half, it can be hard to maintain an uncomfortable position for that long a time. Recurrence of a spinal cord metastases can be treated with stereotactic radiosurgery or surgery but can not be exposed to external beam radiation a second time.
For more on spinal cord compression and metastases, see Selected Bibliography.