Chordomas are locally invasive tumors that arise from the remnant of the primitive notochord. They occur most commonly in the skull base (clivus) and lower spine; approximately 40% of chordomas and chondrosarcomas arise in the clivus. Chordomas are often considered a benign tumor because of their slow growth. However, some chordomas behave aggressively and have more malignant characteristics with extensive invasiveness including a small subset of patients (~10%) that develop metastases to distant sites beyond their site of origin.
Types of Chordoma
There are three histological subtypes of chordoma: conventional (sometimes called classic), chondroid, and dedifferentiated. Chondroid chordomas tend to be less aggressive than conventional chordomas, while dedifferentiated chordomas are more aggressive, faster growing and more likely to metastasize.
Chordomas are often confused with or misdiagnosed as chondrosarcomas, and vice versa. Both types of tumor can occur in the same locations and often look similar under a microscope. Generally, chondrosarcomas tend to be more responsive to radiation and have a better prognosis. Therefore before proceeding with treatment, it is important to get multiple opinions on the pathological diagnosis from experienced pathologists who routinely see both types of tumors.
SYMPTOMSMost patients with a clival chordoma develop headaches and double vision. Less common symptoms include visual loss, hearing loss, difficulty swallowing, facial numbness, in-coordination and motor weakness.
DIAGNOSISThese skull base tumors are best diagnosed by MRI and CT scans which will clearly show the extent of tumor and bony destruction. Focused MRIs of the pituitary region, sinuses, temporal bones or internal auditory canals may be indicated to obtain better anatomical detail of a chordoma. Other tests may also be needed prior to surgery such as angiography (typically now performed as a CT angiogram or an MR angiogram), visual field tests, an audiogram or hormonal tests.
Several different scans are done to locate the tumor. Two of the most common are the computed tomography (CT or CAT) scan and magnetic resonance imaging (MRI). A CT scan uses x-ray images taken from many angles and computer reconstruction to show parts of the body in cross section. This helps to locate and estimate the size the tumor, and provides information on whether it can be surgically removed. MRI uses magnets and radio waves to create more detailed cross-sectional scans than computed tomography. There are many variations on these two scans that use dyes or radioactive materials to provide information about blood flow around the tumor and help determine whether the tumor can be surgically removed.
Currently, surgery is the first-line treatment for chordomas. Complete resection (removing the entire tumor) during the first surgery provides the best chances for local control and long-term survival.To achieve a complete resection, aggressive surgery is often required and can lead to significant complications or side-effects.
The goal of surgery should be to remove as much of the tumor as possible without causing unacceptable harm. Because outcome and prognosis are largely dependent on the success of the initial surgery, before having any operation it is very important to get multiple opinions from surgical teams who have experience treating chordomas on a regular basis. Some medical centers have multidisciplinary teams of experts who review cases and can help create a coordinated treatment plan for patients with chordomas.
RadiotherapyIn many cases, radiation therapy following surgery is recommended and can improve chances of local control and survival. Because chordomas do not grow rapidly, high doses of radiation are required to kill the tumor cells. Chordomas that are close to critical structures (arteries, brain, brainstem, cranial nerves, dura, spinal nerves), often limit the dose of radiation that can be safely delivered to the tumor. In most cases, proton beam radiation can maximize the dose of radiation to the tumor, while sparing adjacent critical structures. Intensity modulated radiation therapy (IMRT), stereotactic radiosurgery and carbon-ion radiotherapy are also sometimes used to treat chordoma.
Chordomas are generally resistant to standard cytotoxic chemotherapy agents, and there are no drugs approved to treat chordoma. Dedifferentiated chordomas are sometimes treated with chemotherapy to kill rapidly multiplying cells. Recently, Gleevec® (imatinib) has been shown to have antitumor effects in some patients with advanced chordomas.Additionally, off-label use of other targeted therapies such as ERBITUX (cetixumab), Iressa (gefinitinib), Tarceva® (erlotinib) have been reported.
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