Chordoma is a rare slow-growing but persistent type of malignant bone tumor (sarcoma) found along the spine. These tumors are thought to grow out of remnants of the notochord, an embryonic precursor to the spinal cord. Chordomas are difficult to eradicate because of their proximity to the spine and their tendency to recur even after complete surgical removal.
Definition & Facts
Chordomas generally develop in the base of the spine (most common), the base of the skull, or in the vertebrae along the spinal axis (least common). Roughly 300 new cases are identified in the United States annually. That represents 0.2% of tumors of the central nervous system that are diagnosed.
Males are about 1.6 times more likely than females to develop chordoma. Chordomas may affect individuals of any age. The median age at diagnosis varies from 49 for tumors at the base of the skull to 69 for tumors at the base of the spine. Five-year survival rate is about 67 percent and ten-year survival rates is approximately 50 percent.
Symptoms & Complaints
As skull-base chordomas grow they may cause cranial nerve disease, which may lead to the loss of control of facial muscles and a decrease or loss of sensation in areas of the face. These large skull-base tumors may also cause symptoms common to chordomas in the neck region (cervical vertebrae) including hoarseness, speech problems, difficulty swallowing, and (rarely) bleeding in the throat.
Patients with tumors along the lower spinal axis may suffer back pain, urinary incontinence, and weakness of the legs. Chordomas in the sacrum (base of the spine) may trigger loss of bowel control (fecal incontinence) as well as tingling, pain, or numbness in the arms and legs. Tumors in roughly half of the individuals with sacral chordomas are large enough to be palpable.
Chordomas appear generally to occur at random. No environmental factors, lifestyle habits, or dietary risk factors have been identified. Known genetic factors for chordomas do not appear to be directly causal. Among chordoma patients who have been tested nearly all exhibit a particular genetic variant of a gene called brachyury. This variant, which is called a single-nucleotide polymorphism (SNP) is also found in a very large number of individuals who never develop chordoma. Rarely, chordoma is found in multiple members of the same family. In some cases of familial chordoma, individuals have extra copies of the brachyury gene.
Chordomas occur at sites within the spinal column that match the sites where remnants of the notochord are found. The notochord is an embryonic structure that is replaced by the spinal column during development. This coincidence between notochord remnants and tumors suggests that genetic mutation of the remaining portions of the notochord is responsible for chordomas. A variety of mutations have been observed in chordomas, but no mutations have been found to be specifically responsible for the development of chordomas.
Diagnosis & Tests
Diagnosis of chordoma often does not occur until the tumor is quite large. Early symptoms of chordoma at the base of the skull (headaches, neck pain, and changes in vision) or at the base of the spine (back ache and pain, numbness, etc. in the arms and legs) are easily confused with more common conditions.
In the case of chordomas at the base of the spine, tumors may first be detected through palpation of a suspicious lump along an individual’s spinal column. Computed tomography (CT) scans, magnetic resonance imaging (MRI) tests, and positron emission tomography (PET) scans all can be used to detect growths along the spinal column. A definitive diagnosis of a suspicious mass may then be obtained through pathological analysis of a biopsy of the tumor.
Metastasis occurs in less than 10% of cases of skull-base tumors and 20-40% of cases of tumors further down the spinal column. Metastasis is typically only seen in advanced cases, where control has either been unsuccessful or untried.
Treatment & Therapy
When feasible, aggressive surgery is recommended to manage chordomas. To minimize the risk of metastasis and to maximize long-term survival, the primary goal of the surgeon is to remove the entire tumor in the first surgery. Complete removal is not always possible because of the proximity of the tumor to the spinal column and other critical elements of the central nervous system.
Studies do not indicate radiation therapy improves either local tumor control or long-term survival for patients where the entire tumor was removed during surgery. Even when removal is complete, recurrence at or near the original location of the removed tumor is common. That being said, radiation therapy may still be recommended following surgery as an adjuvant therapy for complete resection and especially for partial resection of tumor.
Narrowly focused radiation sources, such as proton therapy and carbon ion therapy work better for chordoma treatment than traditional X-ray therapy. Chemotherapy is not generally effective against slow-growing tumors, given that these drugs target fast-growing cells. The FDA has not approved any drugs for the treatment of chordoma, according to the Chordoma Foundation.
Prevention & Prophylaxis