Spinal Metastatic Tumors
Tumors inside the spinal cord itself are often called “intramedullary.” Those outside the spinal cord are “extramedullary.” Tumors outside the cord itself but within the tough cover (the dura) that surrounds the cord are often referred to as “intradural.” Everything outside the dura is “extradural.”
Cancer rarely spreads into the spinal cord itself. In fact, only one to three percent of tumors found in the spinal cord are metastatic. About 50 percent of such tumors are lung cancers and 13 percent are breast cancers, with melanoma (skin cancer), lymphoma (lymph cancer) and renal cell carcinoma (kidney cancer) being other relatively common cancers of origin.
Intradural metastases are also relatively uncommon, accounting for about five or six percent of spinal-area metastases. The vast majority of cancers metastasizing to this region spread to the bones and structures of the spinal column. Cancers of the lung, breast, gastrointestinal tract, prostate gland, lymphatic system (lymphoma) and skin (melanoma) are among those that commonly metastasize to the spine.
A complex system of nerve pathways, the spinal cord controls certain reflexes and instantaneously relays information between the brain and the body. Cancer metastasizing to the spinal cord destroys these vital pathways from within. Cancer in the dura area may cause swelling of tissues, retention of fluid, blood vessel injury and hemorrhage, damage to nerve fibers, and spinal cord distortion.
Cancers metastasizing to the spinal column typically damage the bones and other structures initially, possibly leading to the collapse of vertebrae segments. Neurologic problems occur as the tumor or bone debris press on the spinal cord or nerve roots feeding the nerves going out to the body.
About 70 percent of metastatic spine (bone) tumors are in the thoracic (chest-level) area, while 20 percent of tumors are found in the lumbar (lower back) region and 10 percent are in the cervical (neck) spine. There may be a single tumor isolated in one location, but tumors often are found at several levels, not necessarily next to each other.
Outcomes are variable, based on a number of factors, including the type of cancer, the number of metastases to the spine and other areas of the body, the patient’s overall health, and the degree of injury the metastasis has already inflicted on the spinal cord. If a small tumor in a single location is discovered and treated early, the prognosis may be good, but these tumors often become well established and produce significant damage before causing symptoms and being detected.
The outlook for most cases of metastatic cancer to the spine or spinal cord has historically been poor, with survival often measured in months. It is important to remember, however, that some patients live considerably longer, and new experimental therapies are taking a proactive approach in fighting these tumors. New treatments for a variety of cancers are becoming available and the techniques used to treat spinal disorders have improved.
X-rays can show changes in a patient's spine, but usually not until significant damage has occurred. Magnetic resonance imaging (MRI) is typically the diagnostic tool of choice. Other studies may include computed tomography (CT), which is especially useful for imaging bone, and positron emission tomography (PET) or single photon emission CT (SPECT), which use radioactive tracers to identify active cancer cells in bone.
The choice of treatment is highly individualized, taking each patient’s wishes and many other circumstances into consideration. A team of specialists providing expertise from many perspectives is important in addressing all of a patient’s medical and psychological needs
Because the cancer has metastasized from the original site and may affect other sites as well, treatment of a spinal metastasis is not likely to increase life expectancy. Typically, the treatment used for the original cancer, such as chemotherapy, will be included in treatment for the metastasis.
In many cases, the goals of treatment will be to control pain and preserve as much neurologic function as possible for as long as possible. Patients who are able to walk at the time treatment is initiated – a sign that indicates preservation of a degree of neurologic function – tend to have somewhat better outcomes than those who are not. The loss of a major function, such as walking or bowel and bladder control, is rarely reversible.
For many patients, the first treatment will be high-dose dexamethasone, a steroid that can reduce bone pain. Additional drugs may be given to treat nerve-related pain.
Radiation therapy is the most widely used treatment, although certain types of tumors are resistant. Radiosurgery using the Trilogy system is especially suited for tumors near the spine.
In some cases, surgery will be used in conjunction with radiation therapy. A study released in 2005 found that the addition of surgical intervention with radiation therapy provided better results than radiation alone in treating spinal cord compression caused by metastatic cancer. Patients who underwent both therapies were able to walk a median of 122 days (half of the participants walked more, and half walked less), compared to 13 days for those who only underwent radiation. The results on continence were similar; patients who had the combination of treatments lived a median 126 days, compared to 100 days, and needed less medication to control pain.
While radiation may decrease pain by causing tumor growth to slow and possibly shrink, it does not have the immediate results that surgery may offer. Surgery might also be needed to remove bone debris and rebuild the spine. Depending on the area and extent of damage, a variety of surgical approaches may be used, and these surgeries are often performed in a team effort that includes orthopedic surgeons and neurosurgeons specializing in spine surgery.
Minimally invasive tools and techniques now enable surgeons to perform spinal cord decompression and spinal column reconstruction through small passages, reducing pain and recovery time.
Symptoms of external tumors are somewhat similar, although they generally occur equally on both sides of the body and are caused by compression of nerve roots, the spinal cord, or both.
Compression of nerve roots can cause pain, numbness and tingling in areas of the body served by the connected nerves. Without intervention, this will likely lead to muscle weakness and loss of muscle tissue in the affected areas.
Pressure on the spinal cord causes injury to tissues, which leads to swelling and an accumulation of fluid. As more pressure builds and more nerve tissue dies, sensations decrease and weakness increases in the areas controlled by the spine below the point of injury. The effects can worsen quickly, resulting in loss of bowel and bladder function, as well as paralysis.