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Types of Cancer > Brain Tumors > Overview

Overview of Brain Metastases and Available Treatments

Carolyn Vachani, RN, MSN, AOCN
Affiliation: The Abramson Cancer Center of the University of Pennsylvania
Last Modified: February 26, 2008

Brain Tumors versus Brain Metastases

Differing between these two types of brain lesions is a common source of confusion for many people. Primary brain tumors are tumors that start in the brain, and are actually quite rare, with an estimated 21,810 new cases in 2008. Brain metastases are far more common, and are tumors that have traveled to the brain from another area of the body. It is estimated that more than 170,000 patients develop brain metastases each year.

Let's use an example to better understand this latter concept: a lung cancer is first formed in the lung tissue, but tumor cells can break off from the original mass and travel through the bloodstream or lymph system to other areas of the body, including the brain. This spreading of the tumor is known as “metastasis”. When a lung cancer metastasizes to the brain, this “brain tumor” is actually lung cancer cells.

It sounds odd, but if the pathologist took a biopsy of the brain lesion and looked at it under a microscope, it would look like lung cancer cells. It is important to understand the difference between primary brain tumors and brain metastases because they are treated differently. I occasionally hear the media refer to a person who died of lung cancer and brain cancer, when, in actuality, it was lung cancer that had metastasized to the brain.

Among tumor types, lung cancers account for the highest number of brain metastases, with 25% of patients being affected at some time in their disease. Other cancers that commonly metastasize to the brain include melanoma, breast cancer, colon cancer, and renal cell (kidney) cancer. Although these are the most likely types to do so, technically any type of cancer could spread to the brain.

All Tumors Are Not Created Equal

One thing to keep in mind is that all cancers are not equal. Some are more aggressive and/or less susceptible to our treatments than others, and for this reason, prognoses vary greatly from tumor to tumor and person to person. These variations are also important to consider when choosing treatments. For instance, primary lung cancers are quite sensitive to radiation, but melanomas are not. This susceptibility to radiation, or radiosensitivity, does not change once the tumor spreads to the brain. In turn, treatment decisions vary based on the primary (original site) tumor type. This holds true for chemotherapy as well. If a primary tumor is sensitive to a particular drug, the brain metastases from that tumor type are more likely to be affected by the same drug. For example, lung cancer is often treated with cisplatin, but breast cancer is not as sensitive to cisplatin, so another drug would be used for brain metastasis from primary breast cancer.

Brain Metastases on the Rise

The oncology community has seen a rise in the number of brain metastases in recent years. Researchers have known for years that many of the chemotherapy agents commonly used are not able to cross the blood-brain barrier, meaning that the drugs are not able to penetrate the brain, and therefore cannot effectively kill cancer cells that make their way to this sanctuary. It is thought that as newer chemo-, bio-, and immunotherapies all become increasingly more effective at treating cancer in the rest of the body, some cancer cells run for cover, so to speak, and hide out in the brain. In turn, there are a limited number of medications for treating brain metastases, and most therapies center around surgical and radiation techniques. We will review the various techniques available and the relevant supporting data.

Unfortunately, in most cancers, once a person develops brain metastases, the tumor is not curable. With current treatments, patients can live from months to years, depending on the number of brain metastases, the type of tumor, and the amount of cancer present in the rest of the body. There are exceptions to this rule in the case of tumors that are highly sensitive to chemotherapy, such as germ cell tumors (testicular), lymphomas, leukemias, and the rare case here and there in other cancer types.