Senator John McCain made headlines after being diagnosed with a glioblastoma, the deadliest of all brain tumors. That grim description makes it sound like it’s over for those who are afflicted.
But survival rates vary widely. Some of these tumors respond better than others to treatment, so it’s important to recognize easy-to-miss symptoms of this disease. Early diagnosis means treatment can start sooner. And while it can’t be cured, there are advances that may improve the odds of living longer.
This cancer is a primary brain tumor—it originates in the brain in contrast to cancers such as lung cancer, skin cancer or breast cancer that start somewhere else and may spread to the brain.
About half of primary brain tumors are benign (not cancerous)—and these have a high cure rate. The rest are malignant and tend to be aggressive and life-threatening. A glioblastoma is both the most common and the most aggressive kind of malignant primary brain tumor. It is a tumor that grows from cells that make up the gluelike supportive tissue of the brain, and tumor cells migrate throughout the brain, so it’s hard for a surgeon to remove it entirely. Average survival after diagnosis is only 18 to 24 months, with 25% of patients alive after two years and 10% alive after five years.
Glioblastomas strike both men and women, often in their 40s, 50s or 60s. Few causes are known—exposure to high levels of radiation to treat a childhood cancer is one, and cell-phone use is a suspected cause (see below). There is rarely an identifiable genetic predisposition. The frustrating reality is that most cases, like Senator McCain’s, are seemingly spontaneous—no one knows what brings them on.
With a glioblastoma, as the malignant cells spread, they increase pressure in the cranium, which leads to headaches in about half of patients. Blurry vision and/or seeing double can also occur. So can mood changes such as sudden-onset depression or anger. Muscle weakness or numbness in the arms and/or legs, which can lead to trouble walking, is another possible symptom. More symptoms…
• Seizures. Brain tumors can interfere with communication between nerve cells, causing abnormal electrical activity that manifests as seizures. Nearly one-third of brain tumor patients will experience at least one seizure. A seizure can range in intensity from a subtle twitching on one side of the body to a loss of consciousness. It may be preceded by an aura, an abnormal change in sensation such as tingling, sensing flickering lights or smelling an unpleasant odor.
• Trouble reading. While memory loss and confusion can be glioblastoma symptoms, some are more specific. Other commonly affected areas of the brain are the frontal, temporal or parietal lobes, which are responsible for language comprehension, math or spatial orientation. If a tumor grows in the left frontal or temporal lobes, a person may have difficulty speaking or understanding others or comprehending sentences containing cross-references or comparisons. With tumors in the parietal lobe, math may become unusually challenging and so may interpreting material shown in formats such as columns or charts—the parietal lobe also governs recognition of left-right or up-down positioning.
Just having one of these symptoms, or even more than one, does not mean that you have brain cancer, of course. One clue is how quickly symptoms come on. With a glioblastoma, several serious symptoms often arise in a matter of weeks or at most a few months.
The first option after discovery of a glioblastoma is often surgery, followed by radiation and chemotherapy. A glioblastoma can’t be cured, but it can be managed to extend life. Some promising newer treatment options now being studied in humans…
• Immunotherapy. A cutting-edge class of drugs known as checkpoint inhibitors ignite the immune system by blocking certain signals released by tumors. That allows tumors to be “seen” and attacked by the immune system. Several clinical trials are now under way to test immunotherapies for glioblastomas.
• Drugs that cross the blood-brain barrier. There is a dense lining of cells that surrounds and protects the brain. Most drugs can’t cross it, including many chemotherapy drugs. But the budding field of nanomedicine—including the use of drugs as tiny as molecules—is leading to investigational agents that breach the barrier, enter tumor cells and block key proteins.
• Brain tumor vaccine. Vaccines containing a patient’s own immune cells—specifically, dendritic cells (cells that identify foreign invaders in the body)—may be able to activate a patient’s immune system to attack the tumor. In a small 2017 study of 16 glioblastoma patients who received such a vaccine plus chemotherapy, published in Clinical Cancer Research, four were still alive after five years. More trials are under way.
On the horizon…
• Blood test before symptoms arise. Changes in tumor protein activity indicative of a future brain tumor may one day be detectable via a blood test.
• Could Zika help? Scientists are exploring whether the Zika virus, which can cross the blood-brain barrier, might in a deactivated form destroy brain tumor cells.
Wireless devices including cell phones emit radiation, which we know can penetrate into the brain and, over time, may cause normal cells to become cancerous. Some studies have found a link between cell-phone use and brain cancer, including glioblastomas. But others have failed to do so. It makes sense to err on the side of caution…
• When speaking on a cell phone, minimize radiation exposure by using wired earphones (not a wireless version) or use the speakerphone function.
• Limit use to areas with good reception, which enables your phone to function at reduced power and therefore with reduced radiation.
