Glioblastoma: Grade IV Tumor
Glioblastoma is considered a grade IV tumor, the most aggressive type. Glioblastoma is not categorized by stages, as cancers usually are.
Glioblastoma, also called glioblastoma multiforme or GBM, is a type of primary brain cancer. It arises in brain cells called astrocytes, a type of supportive (glial) cell that makes up the connecting tissue of the brain. Glioblastoma is a fast-growing cancer that can spread quickly throughout the brain. It does not usually spread to other areas of the body. Doctors classify brain tumors from grade I to grade IV based on their aggressiveness. Glioblastoma is considered a grade IV tumor, the most aggressive type.
Symptoms of glioblastoma are related to pressure in the brain and may include:
- personality or mood changes
- speech difficulties
- eyesight changes
Glioblastoma tumors are challenging to remove completely with surgery. For that reason, they are difficult to cure. However, new approaches and clinical trials are showing promise at delaying when the disease comes back and extending survival.
Surgery is usually the first treatment for glioblastoma. The goals of surgery are to relieve pressure in the brain and to safely remove as much of the tumor as possible. This is done before giving other treatments, such as radiation or chemotherapy.
Glioblastoma tumors typically are found in one of the two halves of the outermost region of the brain, but they can occur anywhere in the brain or spinal cord. These tumors can be hard to remove completely because they tend to have irregular patterns of growth and a complex shape. They may also have microscopic extensions that can work their way into vital parts of the brain, such as the regions controlling speech and motor coordination.
Radiation for Glioblastoma
Radiation therapy is part of the treatment for glioblastoma and typically occurs following surgery. Radiation may be used as the sole treatment when a glioblastoma tumor is located in an area that is not appropriate for surgery. Studies have shown that people live longer when given the combination of surgery and radiation therapy compared with surgery alone.
Radiation is usually given along with a chemotherapy drug called temozolomide (Temodar) that makes the tumor more sensitive to the radiation. Studies have shown this combination to be more effective than radiation without temozolomide.
Radiation can be directed precisely to the tumor, sparing the nearby healthy tissues and leading to better outcomes for patients. We are able to verify within millimeters that the setup for each patient is accurate and can be reproduced from treatment to treatment.
The most common schedule of radiation therapy is daily treatment with a low dose of radiation delivered over six weeks. This amount of radiation is well tolerated by most patients, causing few side effects.
The most common form of radiation delivery is external-beam radiation, in which treatment is delivered from a machine called a linear accelerator. External-beam radiation can be delivered from different angles in higher doses with intensity-modulated radiation therapy (IMRT).
Chemotherapy for Glioblastoma
The chemotherapy drug temozolomide is usually given along with radiation to treat glioblastoma. This drug sensitizes the tumor to the radiation, making the latter more effective. Temozolomide is also continued for a minimum of six months after completion of radiotherapy.
The targeted drug bevacizumab (Avastin) is sometimes used to treat glioblastoma. This drug works by blocking the growth of new blood vessels that nourish the tumor. Bevacizumab is usually used once the tumor returns and can be very effective at easing symptoms. It is rarely used as part of the initial therapy.
Immunotherapy is any treatment that uses the immune system to fight cancer. While no immunotherapies are yet approved by the FDA for the treatment of glioblastoma, several early-stage clinical trials have suggested that immunotherapies might be effective in treating the disease.
Drugs called checkpoint inhibitors, including pembrolizumab (Keytruda) and nivolumab (Opdivo), are being tested in glioblastoma. These drugs work by “releasing the brakes” on the immune system, empowering it to go after and fight cancer.
Another immunotherapy approach that is being tested is therapeutic cancer vaccines. These therapies work by presenting the body with fragments of proteins called antigens that the immune system recognizes as foreign and dangerous. Glioblastoma cells make a number of antigens that are unique to the cancer cells, which makes them attractive targets.
Sometimes, genetically modified viruses are used to kill cancer cells and release cancer-specific antigens.
Chimeric antigen receptor (CAR) T therapies, which give new information to immune cells so they recognize cancer cells as foreign, are also being explored as a treatment for glioblastoma.