Saturday, August 24, 2013

Risk Factors for Chordomas

There are no known environmental, dietary or lifestyle risk factors. Several genetic risk factors listed below are associated with chordoma. 

Brachyury SNP

The vast majority of chordomas are sporadic, meaning that they occur at random, and not as a direct result of an inherited genetic change. However, nearly all patients who develop sporadic chordoma harbor a genetic variant called a SNP in a gene called brachyury . This SNP causes a substantial increase in the risk of developing chordoma, but does not by itself cause chordoma. To use a metaphor, the brachyury SNP loads the gun but something else pulls the trigger. A large fraction of the general population has this SNP but individuals who have the SNP are still very unlikely to develop chordoma. 

Brachyury duplication

Very rarely, multiple members of the same family are affected by chordoma, indicating that in some cases a strong genetic predisposition for chordoma can be inherited. Some families with familial chordoma have an extra copy of a gene called brachyury.  Currently, there is no available test for the presence of extra copies of the brachyury gene.

Tuberous Sclerosis Complex

Chordomas have been reported at a higher incidence in children with the genetic disease Tuberous Sclerosis Complex  (TSC).Changes in either of two genes involved in Tubersous Sclerosis Complex (TSC1 and TSC2) can cause a predisposition to developing chordoma.

Chordoma Location

Chordomas can occur anywhere along the spine, from the head to the tailbone. The most common locations are in the clivus (a bone in the middle of the head) (32%) and sacrum or coccyx (vertebrae at the bottom of the spine) (29%). Less frequently, chordomas can occur in the cervical (neck), thoracic (upper back), and lumbar (lower-back) vertebrae of the spine. Extremely rare cases of chordoma occurring away from the spine have been reported in the ribs, legs and feet.
Chordomas occurring in the head are sometimes called brain tumors because they grow inside the skull toward the brain, however they do not actually develop from brain cells. Metastasis (spread of tumor to other body parts) occurs in 20-40% of patients with chordomas of the spine and less than 10% of patients with skull-base tumors. The most common sites of distant metastasis are the lungs, liver, bones, and skin. Metastasis usually only occurs when the primary tumor is advanced or uncontrolled and rarely is reported at the time of initial diagnosis.

Understanding Chordoma

Chordoma is a rare type of cancer that occurs in the bones of the skull and spine. It is part of a family of cancers called sarcoma, which include cancers of the bones, cartilage, muscles and other connective tissue.
Chordomas are thought to arise from remnants of the embryonic notochord, a rod-shaped, cartilage-like structure that serves as a scaffold for the formation of the spinal column. Notochord cells normally persist after birth lodged inside the spine and skull, and rarely these cells can undergo a malignant transformation that leads to the formation of a chordoma.
Chordomas are generally slow growing, but are relentless and tend to recur after treatment. Because of their proximity to critical structures such as they spinal cord, brainstem, nerves and arteries, they are difficult to treat and require highly specialized care.