Staging

Staging is a way of describing a tumor, such as where it is located if it is cancerous if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the tumor’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of tumors.

After meningioma has been diagnosed, additional tests will be done to learn more about the tumor. There is no formal staging system for meningioma, because CNS tumors cannot be staged the same way as other types of tumors.

For meningioma, doctors use seven factors to establish the course of treatment and to determine prognosis:

Tumor histology/Grading. How a tumor looks under a microscope is called tumor histology. A sample of the tumor is removed during surgery for a biopsy. When surgery is not possible, a biopsy alone is done to obtain the sample.

Using the histology, the doctor can determine the type of tumor and its grade. Grading describes how closely the tumor cells resemble normal tissue under a microscope. To decide on a treatment, both the type and grade of the tumor must be identified.

Normal tissue usually has differentiated tissue (different types of cells grouped together). Tumor tissue that is cancerous is usually made up of cells that look more alike. In general, the more differentiated the tissue and the lower the grade, the better the prognosis.

To determine the histology of a tumor, doctors also look at:

• Mitosis (the number of cells dividing)
  
  
• Hypercellularity (the tumor contains large numbers of cells)
  
  
• Vascular proliferation (blood vessels in the tumor are growing)
  
  
• Necrosis (dead tissue in the tumor)

In general, a meningioma is classified into one of three grades:

• A grade I tumor does not have mitosis or necrosis.
  
  
• A grade II tumor is hypercellular and has mitosis and may have a limited degree of necrosis, but does not invade the adjacent brain. This is usually called “atypical.”
  
  
• A grade III tumor has necrosis and often shows brain invasion. This is usually called “anaplastic.”

Labeling Index using MIB-1 test. This test identifies the percentage of cells in the tumor that are in the process of dividing, called the S phase of division. The more cells that are in that phase, the more aggressive the tumor is. Generally, a slow-growing meningioma has a MIB-1 of less than 5%.

Age of patient. In adults, the age of the patient at the time of diagnosis is one of the most powerful predictors of prognosis. In general, the younger the adult, the better the prognosis.

Extent of tumor residual. Resection refers to surgery to remove a tumor. Residual refers to how much of the tumor was left behind after surgery. Three classifications are used:

• Gross total. The entire tumor was removed (microscopic cells may remain).
  
  
• Subtotal. Only part of the tumor was removed.
  
  
• Biopsy only. Only a small portion, used for a biopsy, was removed.

The outcome is most favorable when all of the tumor can be resected (surgically removed).

Tumor location. Tumors can form in any part of the CNS. Some tumor locations cause greater damage than others, and some tumors are harder to completely remove than others.

Functional neurologic status. The doctor will test how well a patient’s CNS is working by using an assessment called the Karnofsky Performance Scale. A higher score indicates a better prognosis.

Metastatic spread. Meningioma rarely metastasizes to other parts of the body. One reason for this is that a meningioma is more self-contained than a tumor that forms elsewhere in the body. Another reason metastasis does not occur often with brain tumors is due to the fact that the brain does not have a well-formed lymph system to carry cancer cells elsewhere in the body. Cerebrospinal fluid can spread cancer cells, but this is rare with meningioma.

Biogenetic markers

At present, the factors listed above are the best indicators of the prognosis for a person with meningioma. Researchers are currently looking for tumor markers (proteins or other substances found in the blood that can indicate the presence of cancer) in the tumor tissue that could make meningioma easier to diagnose and staging of adult CNS tumor possible in the future. These tools may someday make it possible for doctors to analyze the growth potential of brain tumors, develop more effective treatments, and more accurately predict prognosis.

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.springer-ny.com.