Staging is a way of describing or classifying a cancer based on the extent of cancer in the body. Because most central nervous system (CNS) tumours do not spread, there is no standard staging system for childhood brain and spinal cord cancer. Instead, childhood brain cancers are classified and treated according to their level of risk, their location in the brain or the extent to which they have invaded surrounding tissues.
Cerebellar and cerebral astrocytomas are classified and treated according to their grade.
- Low-grade astrocytomas (Grades 1 and 2) are slow growing and not likely to spread.
- High-grade astrocytomas (Grades 3 and 4) are fast growing and may spread throughout the brain.
Brain stem gliomas
Brain stem gliomas are classified according to the degree to which they have invaded surrounding tissues and their grade.
- Diffuse brain stem gliomas spread freely through the pons (a part of the brain stem deep within the brain). They often spread to other parts of the brain stem (such as the midbrain or medulla) or nearby parts of the brain. They tend to be aggressive, high-grade tumours.
- Focal brain stem gliomas develop in one spot or are contained in a small part of the brain stem (usually the midbrain or medulla). They tend to be less aggressive, low-grade tumours that do not usually spread.
Optic nerve and hypothalamic gliomas
Optic nerve and hypothalamic gliomas are classified and treated according to:
- the location and size of the tumour
- the child's age and general health
- whether or not the child has neurofibromatosis type 1 (von Recklinghausen disease)
- whether or not the cancer has just been diagnosed or has recurred
Ependymomas are classified based on their location and if the cancer has spread (metastasized).
- supratentorial – The tumour is above the tentorium (the membrane that covers the cerebellum).
- infratentorial – The tumour is below the tentorium.
Other factors that help classify ependymomas include:
- whether any cells remain after surgery
- whether the cancer has spread to other parts of the brain and spinal cord
- the age of the child
Medulloblastomas are currently staged in 2 groups based on the level of risk.
A medulloblastoma is considered average risk if:
- The child is older than 3 years of age.
- The tumour is at the very back of the brain.
- All or most of the tumour was removed during surgery (less than 1.5 cubic centimetres remaining).
- The tumour cells have not spread to other parts of the brain or into the CSF. This is determined by a lumbar puncture and MRI scan.
A medulloblastoma is considered high risk if:
- The child is 3 years of age or younger.
- The tumour is not at the very back of the brain.
- Some of the tumour was not removed by surgery (more than 1.5 cubic centimetres remaining).
- The tumour cells have spread to other parts of the brain or into the cerebrospinal fluid (CSF).
Recurrent brain and spinal cord cancer
Recurrent brain and spinal cord cancer means that the cancer has come back after it has been treated. It may recur in the same location as the original cancer or it may recur in another part of the brain or spinal cord. Certain brain tumours, such as medulloblastomas may recur elsewhere in the body, outside of the central nervous system.