Staging is the use of exams and imaging tests to determine how widespread a cancer is. For most types of cancer, the stage (extent) of the cancer is one of the most important factors in selecting treatment options and in determining the outlook (prognosis).
But tumors of the central nervous system (CNS) differ in some important ways from cancers in other parts of the body. The most deadly aspect of other cancers is often their ability to spread throughout the body. Tumors starting in the brain or spinal cord can spread to other parts of the CNS, but they almost never spread to other organs. The most dangerous aspect of these tumors is that they can interfere with essential functions of the brain.
Because most tumors in the brain or spinal cord do not usually spread, they are not formally staged. Some of the most important factors that determine your child's prognosis include:
- The type of tumor (such as astrocytoma, ependymoma, etc.)
- The grade of the tumor (how quickly the tumor is likely to grow, based on how the cells look under a microscope)
- The location of the tumor
- How much of the tumor can be removed by surgery (if it can be done)
- Your child's age
- Your child's functional level (whether the tumor has started to interfere with normal brain functions)
- Whether or not the tumor has spread through the cerebrospinal fluid (CSF) to other parts of the brain and/or spinal cord
- Whether or not tumor cells have spread beyond the central nervous system
Medulloblastoma risk groups
More formal staging systems have been proposed for some childhood brain tumors. For example, many clinical trials for treating medulloblastoma use a system that places children into either standard-risk or high-risk groups. Children are placed in the high-risk group if they are younger than 3, have a lot of tumor that can't be removed during surgery, and/or have cancer cells in the CSF or spread to other parts of the brain or elsewhere. Doctors are still refining this system to make it as accurate as possible.
Recent research has shown that medulloblastoma can be divided into 4 types, based on the major gene changes found in the cancer cells. Each type of medulloblastoma has a different outlook, so doctors may soon be able to use this to better tailor the treatment each child gets (see "What's new in research and treatment for brain tumors in children?").
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