While a cure remains elusive, oncologists are gradually improving the outlook for patients with glioblastoma. Mark Gilbert, MD, chief of the National Institute of Health’s Neuro-Oncology Branch, notes that progress against the disease has been real, but slow. “We have seen incremental improvements in survival. The median length of survival was only 8 to 10 months in the mid-1990s, but it has almost doubled to 15 to 18 months now,” he says. (1) At that time, only a handful of patients lived five years. Now, 15 percent of them do. That’s real progress, but it falls far short of where oncologists would like to be. According to Dr. Gilbert, about 14,000 Americans get glioblastoma each year, most of them active, healthy people. They need better treatments. (1)
What Are Adult Brain and Spinal Cord Tumors?
Brain and spinal cord tumors, like other tumors, are made of abnormal cells that grow out of control. Elsewhere in the body, tumors can be benign — meaning they won’t spread elsewhere in the body — or malignant, which means they will. The malignant tumors are, of course, the most dangerous. In the brain, things are different. Brain tumors do not usually spread to other parts of the body. But they can damage the brain tissue in which they reside, sometimes enough to be fatal. (2)
What Is a Glioblastoma Tumor Made Of?
Many kinds of tissue are found in the brain, and each can give rise to a tumor that’s different from the tumors that occur in other cells. (2) Neurons are the key cells in the brain responsible for thought, memory, emotion, and other higher brain functions. Neurons do not usually give rise to tumors. Glial cells are the supporting cells — the scaffolding that holds things together. There are three types of glial cells, each of which can give rise to tumors:
Oligodendrocytes The first type of glial cells, oligodendrocytes make myelin, a fatty compound that surrounds nerve cell axons — long fibers that carry electrical pulses. Myelin is the insulation, like the rubbery lamp cord or cables that surround and insulate electrical wires in your home. These cells can give rise to oligodendrogliomas.Ependymal Cells The second type of cells line fluid-filled areas in the brain called ventricles. They can give rise to ependymomas.Astrocytes The third type of glial cells, astrocytes help to nourish neurons. They form scar tissue when the brain is damaged. Tumors that begin in these cells are called astrocytomas or glioblastomas.
What Are the Symptoms of Glioblastoma?
The symptoms depend upon where a brain tumor occurs. Some occur in the cerebrum, the large, outer part of the brain, which is responsible for such things as emotion, language, and reasoning, along with vision, hearing, and movement. (2) For example, tumors that arise in the cerebrum can cause seizures, headaches, trouble speaking, a change in personality, and weakness in the body. Tumors in the cerebellum, which lies beneath the cerebrum, can cause problems walking, moving, swallowing, and speaking.
Why Are Glioblastomas So Hard to Treat?
All of these cells and tumors reside behind what’s called the blood-brain barrier, a network of capillaries that create a barrier to keep harmful toxins and infectious organisms from entering the brain. Unfortunately, this makes it harder for chemotherapy drugs to get to the tumors they are designed to fight. Astrocytomas, unlike some other brain tumors, can spread throughout the brain, where they blend with normal, healthy tissue. That makes them difficult to excise with surgery. It’s hard to know where the tumor ends and the healthy tissue begins. If surgeons leave even a few glioblastoma cells behind, those remnants can continue to spread through the brain. A further problem, according to Gilbert, is that glioblastomas are heterogeneous. That is, they contain various populations of cells, some of which respond to treatment and others which do not. These other cells linger and spread through the brain, resulting in little long-term success. (1) And there is more. “The skull being a fixed shell presents another challenge in treating glioblastoma,” says Gilbert. “Cancer therapies may cause tissues to swell. When we treat liver cancer, for example, the liver can swell in the abdominal cavity. But in the case of the brain, there is no place to expand because the skull is a hard shell. We have to be very careful about using treatments that could cause swelling of the brain, and that limits the treatments at our disposal.” (1)
What Will Your Doctor Use to Treat Glioblastoma?
Surgery is often used to treat brain tumors. Radiation and chemotherapy also play a role. The doctors involved in treating brain tumors can include neurologists, oncologists, and endocrinologists, who look for disease in glands that secrete hormones. (3) Doctors will often choose surgery as the first treatment for glioblastoma and other gliomas, although it is usually not entirely successful at removing all of the tumor cells. Radiation therapy is often used as a follow-up to destroy remaining tumor cells, and then chemotherapy. According to the American Cancer Society, the chemotherapy drug used by most doctors is temozolomide (Temodar), because it crosses the blood-brain barrier and can be taken as a pill. Other drugs your doctor might mention are cisplatin (Platinol), carmustine (Gliadel), and lomustine (Gleostine). Combinations of drugs might also be used to treat the tumors. These regimens can slow tumor growth, but are unlikely to cure the tumor. Also, brain tumors that occur in children can be different and require different treatments. (3)
What Does the Future Hold for Treatment of Glioblastoma?
Walter J. Curran, MD, professor emeritus and former executive director of the Winship Cancer Institute at Emory University in Atlanta, is optimistic that progress in treating glioblastoma will continue, despite the difficulties. “There have been substantial improvements in surgical approaches, including new methods of detecting tumor anatomy,” he said in an article published in 2017. That is, new techniques are making it easier to see where the tumor begins and ends, making radiation treatment more effective. Gilbert notes that new techniques under development could improve the outlook for patients with glioblastoma. They include using the body’s own immune system to fight the tumors. “Although the improvements in outcomes have been small and slow, we are optimistic that with continued research efforts, we will discover better, less-toxic treatments and make progress against this disease.” (4)
