Yesterday Senator John McCain’s office announced that he has been diagnosed with a primary brain tumor known as a glioblastoma. The release went on to say that all portions of the tumor visible on imaging have been removed and that the senator and his family were reviewing the next steps. So what exactly is glioblastoma and what are the possible next steps?
What is glioblastoma?
Glioblastoma’s full name is glioblastoma multiforme, often simply called GBM in the medical community. GBM is the most common primary tumor of the brain (primary means that it grows from cells that are in the brain) and occurs at a rate of about two to three per 100,000 adults per year. You may remember that Senator Ted Kennedy also suffered from GBM, eventually succumbing to the disease in 2009.
Unfortunately GBM is one of the most aggressive types of cancer. It is most likely derived from the supporting cells of the brain (not neurons) and the cancer cells grow quickly and send fingerlike projections through the brain. New blood vessels can’t keep up with the growth, they grow abnormally and then parts of the tumor die. This is dangerous in the confined space of the skull because the dead cells lead to inflammation and swelling, which compresses the brain. Without medical treatment, GBM quickly becomes deadly, but with surgery and treatment the median survival time is about 14.6 months. Those who are diagnosed at a younger age tend to live longer and older individuals tend to have a shorter survival time. Reports state that up to 10 percent of people survive five years or longer. As a resident I remember taking care of two patients with GBM that had the disease for about five years.
The most common symptom of GBM, like all brain tumors, is a bad headache. Increased pressure in the brain from the tumor can also cause vomiting and double vision. Depending on where the tumor is growing, different brain functions can also be affected. For example, tumors growing in the front of the brain may lead to personality changes, while tumors near the motor areas of the brain may lead to weakness. Another common symptom of GBM and other brain tumors is seizures.
A surgical specimen and analysis by a pathologist are needed to diagnose GBM, but these tumors tend to have a characteristic appearance on MRI that can make doctors suspicious.
How do you treat GBM?
According to Dr. Michael Lemole, Professor of Surgery and Chief of the Division of Neurosurgery at the University of Arizona, a positive state of mind is important for people diagnosed with GBM. He advises his patients to plan for the worst but shoot for the best, because there are long-term survivors and we are learning more about genetic variations in these tumors that may make them more favorable to treatment.
The goal of treatment for GBM is to control the tumor. The standard treatment is surgery, followed by radiation and chemotherapy. Brain tumors present a unique challenge for surgeons because unlike other types of cancers, you typically cannot remove an entire tumor with wide margins as that would mean sacrificing important brain tissue. After surgery, the go-to chemotherapy agent is called Temozolomide and it has become the standard medication because studies show that it can extend survival by about two months, compared to surgery and radiation alone.
New therapies offer hope.
We’ve talked about immunotherapy on the show for treatment of melanoma and prevention of cervical cancer. GBM is also a target for immunotherapy researchers. While there are many different types of immunotherapy the idea is that these treatments help the body’s own immune system target the cancer cells. This is an advantage over traditional chemotherapy, which involves giving drugs to kill cancer cells. These drugs are typically toxic to healthy cells and tend to result in many side effects.
Currently there are a few immunotherapy drugs in phase III clinical trials (the last phase before FDA approval).
One exciting and surprising new treatment under investigation was recently granted FDA breakthrough status and featured on 60 Minutes. Researchers at Duke University have been using a modified version of poliovirus to treat a small group of patients with GBM. While it is still too soon to know if it will work on a larger scale, researchers have reported that three-year survival on the treatment was about 20 percent.
Another new treatment uses electrical fields to disrupt tumor growth. This FDA-approved technology requires patients to wear electrodes on their head for over 18 hours a day, so it is not convenient, but it has been shown to increase survival.
Lifestyle interventions may also offer some hope, but it is too soon to tell at the moment. Researchers are studying the ability of traditional therapy combined with a ketogenic diet to slow tumor growth. The theory is that some tumors can only rely on glucose for energy and not ketones.
Cancer centers all around the country are studying promising treatments for GBM. To find them you can search here.
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