Chordoma is a rare bone cancer that is diagnosed in only about 1:1.000.000 persons. It develops at the base of the skull, in a vertebra, or at the end of the spine (in the sacrum or the coccyx [the tail bone]) with about equal frequency. The cells that give rise to chordoma come from the notochord. The notochord is an important structure in the early embryo that disappears before birth. However, even after birth, some cells from the notochord remain in bones at the base of the skull, in vertebrae, and in the tail bone. Rarely, one of these cells, which are called notochord remnants, undergoes changes that give rise to a chordoma.
Chordoma is diagnosed most often in people who are in their late 50s, but it can occur much earlier or later. It develops in males more often than females and, for unknown reasons, is rare in African Americans. There are few effective treatments and no cure for chordoma. Most people with chordoma die within 10 years of diagnosis.
A chordoma anywhere along the spine may cause pain, weakness, or numbness in the back, arms, or legs. A chordoma at the base of the skull (occipital chordoma) may lead to double vision (diplopia) and headaches. A chordoma that occurs in the tailbone (coccygeal chordoma) may result in a lump large enough to be felt through the skin and may cause problems with bladder or bowel function.
Chordomas can be difficult to treat because the location of the tumor often makes it inoperable or impossible to remove completely. This is especially true of chordomas located at the base of the skull. When the tumor is inoperable, radiation therapy is the preferred treatment. Proton therapy, also called charged particle therapy, is a type of radiation treatment that spares the tissues around the tumor. For this reason, it is sometimes recommended for chordoma around the skull.
Although chordomas are usually slow-growing tumors, they are locally aggressive with a tendency to infiltrate into adjacent tissues and organs. Local recurrence results in tissue destruction and generally is the cause of death. Metastases are recognized but are uncommon.
Surgery is the preferred treatment for chordomas. Success often depends on the extent and location of the tumor. In general, a more complete removal with wide excision delays the time interval between surgery and eventual recurrence. The natural history and the effectiveness of different kinds of therapy are not well understood in chordomas because of their rare incidence and slow-growing nature.
Radical resections of tumors with clean margins are associated with a longer disease-free interval. If subtotal excision is the only option (generally due to location and proximity to delicate anatomy), the addition of radiation therapy can lengthen the interval to recurrence.
Outcome and Prognosis
Chordomas are relatively benign-appearing neoplasms; however, because of their tendency to erode bone and invade soft tissues, they usually display malignant behavior. In addition, the location of the tumor influences the ability to achieve complete resection. Chordomas often grow in inaccessible sites, and their margins within soft tissue often are not well defined. As a result, complete excision of chordomas is difficult at best.
The 5-year survival rate is estimated to be 51%, and the 10-year survival is estimated to be 35%.
Chordomas are rare neoplasms. As primary intracranial neoplasms, they only constitute 0.2% of all CNS tumors; however, they constitute 2-4% of all primary bone neoplasms. Chordomas generally occur in 3 locations, which are, in descending order of frequency, the sacrum, intracranially at the clivus, and along the spinal axis. Fifty percent of chordomas occur in the sacrum, while spinal axis chordomas are rare. Vertebral chordomas account for only 15% of total chordomas and occur in the lumbar, cervical, and thoracic regions in descending order of frequency.
When considering all locations, the male-to-female ratio is 2:1. However, skull base tumors, as a subgroup, tend to have a more equal sex distribution. A number of reports indicate that chordomas are seen in all age groups, with the peak incidence varying by site. Intracranial chordomas present in a much younger age group than their spinal counterparts because the relevant anatomy of the clival region produces earlier symptomatology. In one series of chordomas reviewed, the average age at diagnosis of all patients with chordomas was 56 years, with an age range of 27-80 years. For chordomas occurring along the vertebrae, the average age is 46 years.
Chordomas are characterized by slow growth, with local destruction of the bone and extension into the adjacent soft tissue. Very rarely, distant metastases are encountered. These tumors usually have a relatively indolent but prolonged course with multiple local recurrences. Eventually, they may be responsible for mortality.
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