McCain's Brain Cancer Diagnosis: A Tough Battle Ahead

The type of brain tumor that doctors removed from Senator John McCain last week is known as a glioblastoma, a highly malignant form of cancer that spreads quickly.

The tumor’s aggressiveness can be attributed to its common location, surrounding and invading the brain’s blood vessels and stimulating the growth of new vessels within and around the tumor. Its cells also tend to spread very quickly along the fibers and tracts throughout the nervous system.

About 12,000 people are diagnosed with glioblastoma each year in the United States. Most die within two years, though some survive more than five years. Mr. McCain is 80 years old.

“Glioblastoma is one of the most malignant brain cancers,” says Vitaly Siomin, M.D., neurosurgeon with Miami Cancer Institute.  “Unfortunately, it often leads to very unfavorable outcomes.”

Mr. McCain’s doctors said in a statement that the tumor was responsible for a small blood clot above the Arizona senator’s left eye, which doctors removed last Friday during a minimally invasive procedure.

Scans completed since last week indicate that Mr. McCain’s doctors were able to remove all the visible tumor tissue.  “The tissue of concern was completely resected by imaging criteria,” the statement from Mr. McCain’s doctors read. They said that Mr. McCain and his family are reviewing treatment options that may include a combination of chemotherapy and radiation.

However, it is virtually impossible to remove glioblastoma tumor cells entirely.

“It may not necessarily affect his life immediately … especially since the surgery (to remove the visible tumor tissue) was done successfully,” says Dr. Siomin. “However, as the disease progresses, and it invariably progresses in the vast majority of patients, it would be very rare for a patient to survive more than 14 months.”

Like with many tumor types, the exact cause of glioblastomas is not known.

Because glioblastomas can grow rapidly, the most common symptoms are usually caused by increased pressure in the brain. These symptoms can include headache, nausea, vomiting, and drowsiness. Depending on the precise location of the tumor, patients can develop a variety of other symptoms such as weakness on one side of the body, memory and/or speech difficulties, and visual changes.

“It is actually quite common to present without symptoms and then have the lesion found incidentally,” says says Dr. Siomin, who is also medical director of the Brain Tumor Program at Baptist Health Neuroscience Center.

But if the tumor continues to grow, symptoms become much more likely, he added. “Patients typically develop some focal/neurological deficits, such as weakness to the point of paralysis,” he said. “They can develop seizures. Other problems could involve personality changes.”

According to the American Brain Tumor Association, glioblastomas represent about 15 percent of all primary brain tumors and about 60-75 percent of all astrocytomas, the type of brain cancer that originates in the “glial cells” of the cerebrum, or the glue-like cells that surround neurons. This type of brain cancer does not usually spread outside the brain and spinal cord. They increase in frequency with age, and affect more men than women. Only three percent of childhood brain tumors are glioblastomas.

Dr. Siomin adds that Mr. McCain may beat the odds, but he has a very tough battle ahead, considering his age and typical responses to post-surgery treatments, including a combination of chemotherapy and radiation.

“Every neurosurgeon has anecdotal cases,” says Dr. Siomin. “We all have patients who survived 5 years, 7 years and even 10 years (after a glioblastoma diagnosis). But these are not typical cases. And most of the patients we see have fairly poor outcomes over that one-year timeframe.”