Brain Cancer Stages: Understanding How Brain Tumors Are Described

When someone is diagnosed with a brain tumor, one of the first questions that might come to mind is about the “brain cancer stages.”

However, it’s important to understand that the way we typically think about “stages” for cancers in other part of the body (like breast cancer or lung cancer) is often different for primary brain tumors.

Instead of a numerical staging system (like Stage 1, Stage 2, etc.), doctors who treat brain cancer primarily use a grading system to describe how aggressive the tumor cells look under a microscope and how likely the brain tumor is to grow and spread to other parts of the brain and spinal cord.

This article will explain why a traditional staging system isn’t commonly used for most primary brain tumors, how the grading system works, and what factors doctors consider when describing the extent and potential behavior of a brain tumor.

We’ll also touch on how secondary brain tumors (cancer that spreads to the brain from elsewhere) are approached.

Why No Traditional Staging for Primary Brain Tumors?

The main reason primary brain tumors don’t typically have a numerical staging system like other cancers is because they rarely spread to other parts of the part of the body outside the central nervous system (brain and spinal cord).

Unlike cancer cells from, say, lung cancer, which can easily travel through the bloodstream or lymphatic system to form new tumors in distant organs, primary brain tumor cells tend to stay within the confines of the brain and spinal cord.

Therefore, the focus shifts from the extent of spread outside the original organ to the characteristics of the tumor cells themselves and how much they have invaded the surrounding brain tissue. The grading system provides this crucial information.

The Brain Tumor Grading System

The most widely used grading system for primary brain tumors is the one developed by the World Health Organization (WHO). This system classifies tumors into four tumor grades, based on how abnormal the tumor cells appear under a microscope and how quickly they are likely to grow:

• Grade I: These tumors are considered the least aggressive. The tumor cells look very similar to normal brain cells, and these tumors tend to grow slowly (tumor grows slowly) and are often associated with a better long-term outcome, especially if they are benign brain tumors and can be completely removed with surgery radiation therapy. Examples include pilocytic astrocytoma.
• Grade II: These tumors are also considered relatively slow-growing compared to higher grades, but their cells look slightly more abnormal than Grade I tumors. They have a higher chance of recurring after treatment options and may eventually progress to a higher grade over time. Diffuse astrocytoma is an example.
• Grade III: These tumors are malignant, meaning they are cancerous and more aggressive. The tumor cells look distinctly abnormal and are growing quickly. These tumors are more likely to invade surrounding brain tissue and recur after treatment. Anaplastic astrocytoma is a Grade III tumor.
• Grade IV: These are the most aggressive and malignant primary brain tumors. The tumor cells are highly abnormal and are growing quickly and spreading rapidly within the brain tissue. Glioblastoma (GBM) is the most common and aggressive Grade IV type of brain tumor.

The tumor grade is a critical factor in determining the appropriate treatment options and predicting the likely outcome (prognosis) for someone with a primary brain tumor.

It’s determined after a brain cancer biopsy, where a sample of the tumor tissue is examined by a neuropathologist.

Factors Beyond Grading

While the grading system is paramount for primary brain tumors, doctors also consider other important factors to fully understand the situation:

• Type of Brain Tumor: As we explored in our article on types of brain cancer, different types of tumors (e.g., gliomas, meningiomas, pituitary tumors) have their own typical behaviors and prognoses, even within the same grade.
• Location of the Tumor: Where the tumor grows in the parts of the brain is crucial. A low-grade tumor in a critical area might still cause significant problems and require aggressive treatment options, while a higher-grade tumor in a less critical area might be more amenable to surgical removal.
• Size of the Tumor: Larger tumors can cause more pressure and symptoms and may be more challenging to treat.
• Overall Health of the Patient: The patient’s age, general medical condition, and immune system strength can influence treatment options and how well they might tolerate them.
• Extent of Invasion: How much the tumor cells have infiltrated the surrounding brain tissue can impact the feasibility of surgical removal and the likelihood of recurrence.
• Genetic Markers: Certain genetic changes within the tumor cells can provide additional information about how the tumor is likely to behave and its potential response to specific treatment options.

Secondary Brain Tumors

When cancer spreads to the brain from another part of the body, it’s called a secondary or metastatic brain tumor. In these cases, the cancer is still named after its original location (e.g., lung cancer that has metastasized to the brain). While the grading of the original cancer is important, there isn’t a separate staging system specifically for how far the cancer has spread within the brain itself. Instead, the focus is on:

• The type of primary cancer: Different primary cancers have different propensities to spreads to the brain.
• The number and location of brain metastases: Are there single or multiple tumors? Where are they located in the parts of the brain?
• The extent of disease elsewhere in the body: The overall burden of the primary cancer and any other metastases is a significant factor in determining treatment options and prognosis.
• The patient’s overall health and neurological function.

Treatment for secondary brain tumors often involves addressing both the tumors in the brain (with surgery radiation therapy, chemotherapy, or targeted therapy) and the primary cancer.

The Darren Daulton Foundation’s Role

Understanding the nuances of how brain tumors are described, including the grading system and other important factors, can be overwhelming for patients and their families. The Darren Daulton Foundation is committed to providing support and resources to those navigating a brain tumor diagnosis.

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While primary brain tumors are not typically staged like other cancers, the grading system developed by the World Health Organization provides crucial information about the aggressiveness of the tumor cells.

Doctors consider the tumor grade along with the type of brain, location, size, overall health of the patient, and other factors to determine the best treatment options and provide an understanding of the likely outcome.

For secondary brain tumors, the focus is on the primary cancer and the extent of its spread.

Understanding these distinctions is an important step in navigating the complexities of a brain tumor diagnosis.