Brain Tumor: Grades and Prognostic Factors

Approved by the Cancer.Net Editorial Board, 03/2023

ON THIS PAGE: You will learn about how doctors describe a brain tumor’s growth or spread. This is called the grade. You will also learn about the prognostic factors doctors use to help plan treatment. Use the menu to see other pages.

What is cancer staging?

For most other types of tumors in other parts of the body, a staging system is used to describe where a tumor is located, if or where it has spread, and whether it is affecting other parts of the body. However, there is no recommended systemic staging system for adult brain tumors because most primary brain tumors do not usually spread beyond the central nervous system (CNS). The grading system described below is always used instead because the specific features of a brain tumor determine how cancerous it is and how likely it is to grow.

Prognostic factors

To decide on the best treatment for a brain tumor, both the type and grade of the tumor must be determined. There are several factors that help doctors determine the appropriate brain tumor treatment plan and a patient's prognosis, which is the chance of recovery:

  • Tumor histology. As outlined in the Diagnosis section, a sample of the tumor is removed for analysis. Tumor histology includes finding out the type of tumor, the grade, and additional molecular features that predict how quickly the tumor can grow. Together, these factors will help your doctor understand how the tumor will likely behave. These factors may also help determine your treatment options.

    Prior to 2021, brain tumors were defined by grades (1 to 4) based on how the tissue looked under a microscope. This grade indicated whether a tumor was growing slowly or quickly. As described in the Introduction, in 2021 the World Health Organization released a new classification and grading system that uses specific features to describe whether a tumor will grow slowly or quickly. These features include whether there is an IDH mutation, high rate of cell division (called the mitotic index), alterations in the CDKN2A/B genes, loss of chromosome 10, gain of chromosome 7, a TERT promoter mutation, and increased number of copies of the EGFR gene.

  • Age. In adults, a person’s age and level of functioning, called functional status (see below), when diagnosed is one of the best ways to predict a patient’s prognosis. In general, younger adults have a better prognosis.

  • Symptoms. The symptoms a patient has and how long they last may also help determine prognosis. For example, seizures and having symptoms for a long time are linked with a better prognosis.

  • Extent of tumor residual. Resection is surgery to remove a tumor. Residual refers to how much of the tumor remains in the body after surgery. A patient’s prognosis is better when all of the tumor can be surgically removed. Whenever possible, surgery to remove all or most of the tumor should be considered if the surgical team and the patient feel the risk of such a surgery is acceptable. There are 4 classifications:

    • Gross total: The entire tumor that could be seen was removed. However, microscopic cells may remain.

    • Near total or subtotal: Large portions of the tumor were removed.

    • Partial: Only part of the tumor was removed.

    • Biopsy only: Only a small portion was removed and used for diagnostic tests.

  • Tumor location. A tumor can form in any part of the brain. Some tumor locations cause more damage than others, and some tumors are harder to treat because of their location.

  • Molecular features. Certain genetic mutations or changes to the genes found in the tumor may help determine prognosis. These include: IDH1, IDH2, MGMT, BRAF, H3K27M, and a 1p/19q codeletion. Sometimes, whether a tumor has any of these mutations or changes determines the type of brain tumor that is diagnosed.

  • Functional neurologic status. The doctor will test how well a patient is able to function and carry out everyday activities by using a functional assessment scale, such as the Karnofsky Performance Scale (KPS), outlined below. A higher score indicates a better functional status. Typically, someone who is better able to walk and care for themselves has a better prognosis.

    • 100: Normal, no complaints, no evidence of disease

    • 90: Able to carry on normal activity; minor symptoms of disease

    • 80: Normal activity with effort; some symptoms of disease

    • 70: Cares for self; unable to carry on normal activity or active work

    • 60: Requires occasional assistance but is able to care for needs

    • 50: Requires considerable assistance and frequent medical care

    • 40: Disabled, requires special care and assistance

    • 30: Severely disabled; hospitalization is indicated, but death not imminent

    • 20: Very sick, hospitalization necessary; active treatment necessary

    • 10: Approaching death, fatal processes progressing rapidly

  • Metastatic spread. A tumor that starts in the brain or spinal cord, even if cancerous, rarely spreads to other parts of the body in adults, but it may grow within the CNS. For that reason, with few exceptions, tests looking at the other organs of the body are typically not needed. A tumor that does spread to other parts of the brain or spinal cord is linked with a poorer prognosis.

  • Recurrent tumor. A recurrent tumor is one that has come back after treatment. If the tumor does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.

Currently, the factors listed above are the best indicators of a patient’s prognosis. As discussed in Diagnosis, researchers are currently looking for biomarkers in the tumor tissue that could make a brain tumor easier to diagnose and allow for the staging of an adult brain tumor in the future. Researchers are also looking at other genetic tests that may predict a patient’s prognosis. These tools may someday help doctors predict the chance that a brain tumor will grow, develop more effective treatments, and more accurately predict prognosis.

Used with permission of the American College of Surgeons, Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017), published by Springer International Publishing.

Information about the tumor’s grade, as well as the prognostic factors, will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.