Our brains are made up of 100 billion cells called neurons, as well as trillions of support cells called glia. Sometimes, during the life cycle of these cells, things can go wrong—changes in your DNA, known as mutations, can cause abnormal cells to grow. When these abnormal cells divide uncontrollably and then gang up together, a tumor forms. A tumor in the brain can be benign (not cancer) or malignant (cancer).

In the U.S., about 80,000 new tumors occur each year in the brain or another part of the central nervous system (CNS), such as the spinal cord. “One half of these are cancerous,” says Yale Medicine’s Veronica Chiang, MD, a neurosurgeon and director of the Gamma Knife Center, "and the incidence of brain cancer seems to be on the rise."

The majority of brain cancers are metastatic (meaning they start somewhere else in the body and spread to the brain), but some are primary (they originate in the brain). Though some cases are inherited, it’s unclear what’s behind most primary brain cancers. Evidence suggests that increasing age and exposure to ionizing radiation, used in some cancer treatments, are risk factors. Investigations of other factors, like diet and cell-phone use, have been inconclusive.

Treatment can include surgery, radiation therapy and chemotherapy or some combination of these options. At Yale Medicine, an individual treatment plan is developed for each patient with input from multiple specialists who meet weekly to discuss cancer cases.

There are over 120 types of primary brain and CNS tumors.

Meningiomas—tumors that arise in the meninges (tissues covering the brain and spinal cord)—are the most common, accounting for more than 35 percent of all primary brain tumors. These tend to be benign but are included in this category because, even though they’re not cancerous, they can compress areas of the brain or nearby veins, causing problems similar to those created by malignant tumors.

As for primary brain cancers, about 80 percent are gliomas, which are tumors that start in the glial cells of the brain. Glioma subtypes include astrocytomas, oligodendrogliomas, and ependymomas. For these and other brain cancers, the World Health Organization has developed a grading system, ranging from Grade I (least malignant) to Grade IV (most malignant), which doctors use to guide decisions about treatment.

The average brain tumor patient is around 60 years old at diagnosis. However, some types of primary tumors, like ependymomas and medulloblastomas, specifically affect children. Pituitary adenomas, tumors that form in the pituitary gland (which is in the skull below the brain), may occur in women of childbearing age. Metastatic brain cancers are most common in older adults and are most often found in patients with cancers of the breast and lung, though they can be associated with almost any type of cancer in the body.

Symptoms can vary widely depending on the part of the brain that’s involved. Of particular concern, says Dr. Chiang, are “persistent and worsening headaches, new development of seizures or new onset of neurological problems that mimic a stroke.”

Other symptoms include but are not limited to:

• Seizures
• Vision problems
• Changes in personality, behavior or mood
• Changes in speech or hearing
• Dizziness
• Difficulty with walking or movement
• Numbness or tingling
• Weakness

Unfortunately, early stage brain cancer often presents no noticeable symptoms. "Depending on the part of the brain in which the tumor grows and the rate of cancer growth, tumors can go undetected for a while, with patients having few or no symptoms," Dr. Chiang says. For patients who have had a prior cancer diagnosis, yearly screenings using magnetic resonance imaging (MRI) or computed tomography (CT) scans of the brain can help find these brain cancers before they become large or cause symptoms.

Doctors perform a series of tests to diagnose suspected brain tumors.

First, they perform a physical and neurological exam. This includes simple tests—like assessments of motor skills and senses—that may help to identify the part of the brain or CNS that’s involved.

Next, diagnostic images (most commonly MRI or CT scan) are obtained to confirm that a tumor exists, and if it does, to evaluate its location, size and effect on surrounding tissue. Sometimes, a positron emission tomography (PET) scan, which can tell how your tissues and organs are functioning, is used to check for cancer. Before a PET scan is obtained, a radioactive substance (tracer) is injected into the patient’s vein—that tracer enables cancer cells to stand out on the image.

Finally, a sample of the tumor is collected either at the time of tumor removal or by a less invasive technique called stereotactic biopsy, in which the doctor inserts a needle into a targeted area of the brain. A pathologist studies the tumor tissue under a microscope to determine whether it’s cancer and, if it is, what type.

Doctors take all these steps to ensure they get the right diagnosis—the treatment strategy hinges on the type of tumor and how aggressively it is likely to behave.

Several approaches may be taken to prevent a malignant brain tumor from growing and spreading into other areas of the brain. Although benign brain tumors aren’t cancer, they can still cause the symptoms mentioned above, based on the area(s) of the brain they are compressing, so these require treatment, too.

Surgery is often the first line of treatment for benign tumors, primary malignant tumors and large metastatic cancers that are causing symptoms or compressing surrounding brain tissues. A neurosurgeon works to remove as much of the tumor as possible while preserving brain function. When the tumor is hard to reach, it is sometimes removed only partially or not at all. Following surgery, patients are often also treated with chemotherapy drugs and radiation therapy. For small metastases that are found before symptoms start to show, stereotactic radiosurgery is usually the only treatment needed. 

At Yale Medicine, our multidisciplinary teams work closely together and communicate frequently to ensure that patients receive the best care for their cancers based on the latest medical evidence. “We are interested in being pioneers, moving the field forward and developing the next steps to further improve care in order to prolong survival, as well as improve every patient’s quality of life,” says Dr. Chiang.  

Yale Medicine has the benefit of working closely with the Yale Genetics Center and many basic science laboratories. This means that patients with no remaining standard care options have the opportunity to be considered for clinical trials where they may be eligible to receive new drugs or treatment.

“More avenues of research are allowing us to develop new approaches to cancer treatment for our cancer patients,” says Dr. Chiang.