Chordoma

Chordoma is a rare slow-growing neoplasm thought to arise from cellular remnants of the notochord. The evidence for this is the location of the tumors (along the neuraxis), the similar immunohistochemical staining patterns, and the demonstration that notochordal cells are preferentially left behind in the clivus and sacrococcygeal regions when the remainder of the notochord regresses during fetal life. Chordoma is a rare slow-growing neoplasm thought to arise from cellular remnants of the notochord. The evidence for this is the location of the tumors (along the neuraxis), the similar immunohistochemical staining patterns, and the demonstration that notochordal cells are preferentially left behind in the clivus and sacrococcygeal regions when the remainder of the notochord regresses during fetal life. Chordomas can arise from bone in the skull base and anywhere along the spine. The two most common locations are cranially at the clivus and in the sacrum at the bottom of the spine. A small number of families have been reported in which multiple relatives have been affected by chordoma. In four of these families, duplication of the brachyury gene was found to be responsible for causing chordoma. A possible association with tuberous sclerosis complex (TSC1 or TSC2) has been suggested. In 2015 the first consensus guidelines for the diagnosis and treatment of chordoma were published in The Lancet Oncology. There are three histological variants of chordoma: classical (or 'conventional'), chondroid and dedifferentiated. In most cases, complete surgical resection followed by radiation therapy offers the best chance of long-term control. Incomplete resection of the primary tumor makes controlling the disease more difficult and increases the odds of recurrence. The decision whether complete or incomplete surgery should be performed primarily depends on the anatomical location of the tumor and its proximity to vital parts of the central nervous system. Chordomas are relatively radioresistant, requiring high doses of radiation to be controlled. The proximity of chordomas to vital neurological structures such as the brain stem and nerves limits the dose of radiation that can safely be delivered. Therefore, highly focused radiation such as proton therapy and carbon ion therapy are more effective than conventional x-ray radiation. There are no drugs currently approved to treat chordoma, however a clinical trial conducted in Italy using the PDGFR inhibitor Imatinib demonstrated a modest response in some chordoma patients. The same group in Italy found that the combination of imatinib and sirolimus caused a response in several patients whose tumors progressed on imatinib alone.