Use of
Gamma Knife technology for chordomas and chondrosarcomas

Chordomas

Chordomas are very rare tumors in the skull base or in the spine. They originate from cell residue of the notochord. The notochord plays an important role in embryonic development of the skull base and spine and normally disappears as the embryo develops. Occasionally you may find that a chordoma develops from remaining cell clusters, which are most common in the head and the sacrococcygeal region. Chordomas are benign tumors that nevertheless grow aggressively locally.

Chondrosarcomas

Chondrosarcomas are very rare tumors that originate from cells that play a key part in forming cartilage. They can develop in the brain and the body, such as the spine, and include malignant cartilage components in the tumor.

Diagnosis

Diagnosis requires CT imaging to show the changes in the bone or instabilities as well as MRI imaging to show the tumor’s soft tissue components.

Chordomas and chondrosarcomas are slow-growing tumors. Both may occur in the region of the skull base. As they grow, they destroy bone and push or enclose surrounding structures such as the brainstem or cranial nerves. This leads to the clinical symptoms such as double vision, dysphagia (difficulty in swallowing), headaches, sensory or motor deficits of limbs.

Chordomas

Epidemiologically the literature reports the annual rate of new cases of chordomas as around 0.2–0.5 per 100,000 people. Chordomas make up 0.1–0.7% of all intracranial brain tumors. With regard to tumor location of all chordomas, around 50% affect the spine, particularly the coccyx, and only a third affect the skull base. The most common age for disease onset is the fifth and sixth decades.

Chondrosarcomas

Epidemiologically, chondrosarcoma is the third most common bone tumor after multiple myeloma and osteosarcoma. Cases affecting the brain peak in the second decade of life. The literature reports 80% of cranial chondrosarcomas on the skull base. Chondrosarcomas account for around 6% of all skull base tumors. The current WHO classification for this tumor is divided up into I.–III.

The primary therapeutic strategy for chordomas or chondrosarcomas is preferably radical surgical tumor removal. This is only possible on the brain in very few cases given the anatomical circumstances. Radiation therapy or radiosurgery is recommended after surgery. However, chordomas or chondrosarcomas are highly resistant to radiation.

Highly focused stereotactic radiation exposure, e.g. with the Gamma Knife or treatment using heavy ions or protons is particularly effective. Here you can target the tumor with high-energy radiation while sparing the surrounding tissue.

There is no reliable therapeutic drugs-based approach; the effectiveness of new immunomodulators for very rare tumors has not yet been sufficiently tested.

Preparation

As part of preparation, the current cranial CT and cranial MRI images help determine treatment options using the Gamma Knife. The key here is to apply as high an energy dose as possible to the residual tumor and to spare the surrounding healthy tissue. The size of the volume to be irradiated is clearly also important.

Radiation therapy

A cranial MRI is conducted on the day of treatment and used for the treatment, along with any previous images. To guarantee high accuracy the patient’s head must be fixed with a stereotactic ring. This is done with local anesthesia and a sedative. The radiosurgery itself is painless and carried out on a single day as an outpatient.

Follow up treatment

Follow up treatment involves a repeat MRI scan around three months after treatment. The checkup intervals are then extended depending on the results.

In the literature the outcome after Gamma Knife treatment is promising and well documented.