Adult Brain Tumors: Grading and Treatment

Author: OncoLink Team
Last Reviewed: 十二月 14, 2022

What is grading for brain tumors?

Primary brain tumors (tumors that start in the brain) do not have a classic staging system like most cancers. Brain tumors are given a grade. This is because the size of a brain tumor is less important than where it is found and the type of brain cell it is made of. These cancer cells are looked at under a microscope to see what kind of cell they are and to give the tumor a grade.

Brain tumors are classified by both the cell that makes them up and how the tumor looks under a microscope. Primary brain tumors can start from any of the cells in the brain. They can come from the neurons, the glial cells, the lining of the brain, or from specific structures in the brain.

How are brain tumors classified and graded?

The most common classification system for brain tumors is the World Health Organization (WHO) system. It classifies brain tumors according to histology (how cells look under the microscope) as well as tumor grade. The WHO numerical grade shows the chance of malignancy (or aggressiveness) from I (benign) to IV (malignant).

Detailed Grading System from the World Health Organization

  • Grade I: Slow growing and almost look normal under a microscope.
  • Grade II: Relatively slow-growing cells, with a slightly abnormal appearance. These can grow into normal tissue and can recur (come back) as a higher-grade tumor.
  • Grade III: Actively reproducing abnormal cells that look abnormal under a microscope. There is invasion of nearby normal tissue and the tumor tends to recur at a higher grade.
  • Grade IV: Abnormal cells reproduce rapidly and have a very abnormal appearance under a microscope. The tumors form new blood vessels to keep growing and there may be areas of necrotic (dead) tissue in the middle of the tumor.

There are many types of brain tumors. Some are malignant (cancerous) while others are benign (not cancer). Both can be hard to treat because the brain is within the skull and tumors can cause pressure on the brain. This pressure is often what leads to symptoms of brain tumors.

How are brain tumors treated?

Treatment for a brain tumor depends mostly on where the tumor is found. Your treatment may include some or all of the following:


Surgery is a treatment option depending on the where the tumor is in the brain. Some parts of the brain are risky to operate on and it may not be safe to do surgery. A neurosurgeon, a doctor who does surgery on the brain, will be able to answer any questions you may have about surgery as treatment.


Chemotherapy is the use of anti-cancer medications to kill cancer cells. On Chemotherapy that is used to treat brain tumors has to be able to cross the blood brain barrier. The blood brain barrier is a natural barrier between the brain and the blood. This barrier blocks things from entering the brain, like some chemotherapies. Some medications that can be used are temozolomide, carmustine, lomustine, carboplatin, cisplatin, etoposide, and bevacizumab.

Brain tumor cells will be tested for specific mutations. If your brain tumor has a specific mutation, you may be able to receive targeted therapies like dabrafenib, trametinib, vemurafenib, cobimetinib, and everolimus to treat your tumor.

Steroids, like dexamethasone, decrease swelling that is caused by the tumor itself or treatment. Decreasing swelling takes pressure off the brain and may lessen symptoms and side effects.

Chemotherapy wafer implants may be used after surgery. The implants look like seeds or wafers and have chemotherapy in them, like carmustine. The implant is placed at the site of the tumor after it is removed during surgery. Chemotherapy is then released directly into the site as the wafer dissolves.


Radiation is the use of high-energy x-rays to kill cancer cells. There are a few different types of radiation that can be used to treat brain tumors. External radiation is radiation that enters the tumor from an outside source and includes intensity modulated radiation (IMRT), proton therapy, and stereotactic radio surgery. Internal radiation, also called brachytherapy, is placed into the body and releases radiation.

  • Intensity Modulated Radiation Therapy (IMRT): This type of radiation limits the dose of radiation received by healthy and important structures (the nerves of the eye, brainstem) near the tumor, limiting damage to healthy parts of the brain.
  • Proton Therapy: This type of radiation enters the body at a fairly low dose and increases closer to the tumor. The beam then stops so that the area behind the tumor does not receive any radiation. Proton therapy tends to lead to less toxicity in the tissues near the tumor.
  • Stereotactic Radio Surgery: Radiation is delivered by several beams from different angles at one time. This provides a large dose of radiation at one time.
  • Brachytherapy: Seeds that have radiation in them may be placed at the tumor site during surgery. They deliver the radiation and do not need to be removed. There is also a small balloon that can be placed during surgery. A few weeks after surgery it is filled with liquid radiation. After a few days of radiation, the balloon and liquid are removed.

Active Surveillance

If your tumor is found early and is growing slowly, it may be best to not start treatment right away. You will be closely monitored during this time to see what your tumor is doing. This is called active surveillance. It is important to let your provider know right away if you have any new or worsening symptoms.

Clinical Trials

You may be offered a clinical trial as part of your treatment plan. To find out more about current clinical trials, visit the OncoLink Clinical Trials Matching Service.

Making Treatment Decisions

Your care team will make sure you are included in choosing your treatment plan. This can be overwhelming as you may be given a few options to choose from. It feels like an emergency, but you can take a few weeks to meet with different providers and think about your options and what is best for you. This is a personal decision. Friends and family can help you talk through the options and the pros and cons of each, but they cannot make the decision for you. You need to be comfortable with your decision – this will help you move on to the next steps. If you ever have any questions or concerns, be sure to call your team.

You can learn more about brain tumors at

American Cancer Society. Adult Brain and Spinal Cord Tumors in Adults.

Dorsey J.F., Hollander A.B., Alonso-Basanta, M., Macyszyn, L., Bohman, L., Judy, K.D., Maity, A., Lee, J.Y.K., Lustig, R.A., Phillips, P.C., Pruitt, A.A., (2014). Cancers of the Central Nervous System. Niederhuber: Abeloff's Clinical Oncology, 5th edition. Philadelphia, PA: Churchill Livingstone, pp. 938-1001.

Louis, D. N., Perry, A., Reifenberger, G., Von Deimling, A., Figarella-Branger, D., Cavenee, W. K., ... & Ellison, D. W. (2016). The 2016 World Health Organization classification of tumors of the central nervous system: a summary. Acta neuropathologica, 131(6), 803-820.

McNeill, K. A. (2016). Epidemiology of brain tumors. Neurologic clinics, 34(4), 981-998.

Merrell R. Brain Tumors. (2015) Section 10: The Nervous System. In, Bope, E. T., & Kellerman, R. D. Conn's current therapy 2016. Elsevier Health Sciences, pp. 647-724.

Mizumoto, M., Yamamoto, T., Ishikawa, E., Matsuda, M., Takano, S., Ishikawa, H., ... & Tsuboi, K. (2016). Proton beam therapy with concurrent chemotherapy for glioblastoma multiforme: comparison of nimustine hydrochloride and temozolomide. Journal of neuro-oncology, 130(1), 165-170.

National Comprehensive Cancer Network. Central Nervous System Cancers. Retrieved from

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