Brain cancer is a disease that affects all ages and all races.
The death this week of Beau Biden, the son of the Vice President and an accomplished man in his own right, has shined a light on this terrible disease.
First, a few clarifications. Properly used, the very word cancer implies a malignant condition, that is, an aggressive disease in which abnormal cells grow with little restraint. Cancer is a diverse disease, some forms more treatable than others, but what all have in common is a genetic modification that allows unimpeded growth and an apparent lack of stickiness. Normal cells have a quality of stickiness that allows them to adhere to each other during the growth process. When things become too crowded, growth slows and stops. Tumor cells lack both the stickiness and the signal that stops growth. In vitro, which means in a petrie dish, these abnormal cells will grow into heaps of cells that die only when they outstrip their nutrient supply. In the body—in vivo—cancer cells overgrow and easily break apart from each other and migrate—called a metastasis—to other areas of the body (either through the blood or via invasion of local tissue). Think of these migrating cells as seeds in the wind. Where they might land is anybody’s guess, but when they find fertile soil (inside the brain or the liver or the lung, etc.), they grow and the whole process starts all over again.
Incidentally, certain patterns are recognizable in how cancer cells metastasize through the body. It’s not really anybody’s guess where they might land. We’ve learned a great deal about the process of metastasis over the years. For example, one can think of the lungs as a great filter through which these cancer cells must pass. Why do cancer cells from the rest of the body have to pass through the lungs? Because of the way the circulatory system is organized. The heart is divided into two halves. The left side sends blood throughout the body with each squeeze. This is oxygenated blood. Where does it get the oxygen? From the lungs, and it’s the job of the right side of the heart to send it’s entire output there. The returning blood, oxygenated blood, enters the left side of the heart and is eventually squeezed out to all points but the lungs.
With the above in mind, it’s easy to imagine the lungs being inundated with cells from all over the body. Some of these will be tumor cells and will grow into metastatic cancer balls. Once in the lungs however, these “mets” are free to break off into the now oxygenated blood returning to the left side of the heart—and then to all points north, including the brain. This is very common and it’s why brain mets often are a harbinger of a cancer out of control. If the cancer has made it to the brain, it can make it anywhere.
Brain tumors may be either malignant or benign. Benign tumors neither metastasize nor invade local tissue, and so, in theory at least, are curable with surgical excision alone. Unfortunately, even benign tumors inside the head are not always accessible to the surgeon and so as they expand they may cause trouble, and even death.
Malignant brain tumors, aka brain cancers, come in a variety of forms. The most common malignant brain tumor isn’t actually from the brain—it’s the metastasis alluded to above, a tumor from elsewhere in the body. Generally, these metastatic intracranial lesions can be controlled with surgery or radiation. But as noted above, they are often an indication the original disease hasn’t been controlled. Death often results from progression of the original disease and not the brain metastases.
Primary malignant brain tumors, commonly referred to as brain cancer, are generally malignant tumors of the supporting substance of the brain, the glial cells. The most common glial cell is the astrocyte, which produces a tumor called an astrocytoma. When somebody speaks of a primary brain tumor that is a cancer, it is often an astrocytoma they are referring to. They come in four general varieties, grade I to grade IV, which in truth smear into one another. The higher the grade, the more malignant the tumor and the worse the prognosis. Grade IV astrocytomas generally become more common with advancing age but certainly do occur with some frequency after the age of thirty or so. Grade I and II are more common in younger people and children. Unfortunately, these lesser grade tumors often occur in areas where their removal is difficult or impossible. They are very slow growing however, and associated with many years of survival. Cure is possible in many cases.
The Grade IV astrocytoma is also known as glioblastoma multiforme, or GBM for short. It is the bane of the neurosurgeon’s existence because it is invariably fatal. It rarely metastasizes, but is highly aggressive in invading surrounding brain tissue and cannot be cured with surgery alone. Treatment involves a combination of surgery, radiation, and chemotherapy. Survival is measured in months to a year or longer. Sometimes much longer. GBM is one of the most malignant tumors the body is capable of producing. This is likely the kind of tumor that killed Beau Biden, as well as Sen. Ted Kennedy. It is also the tumor that likely killed William J. Casey, Director of the CIA during the Iran-Contra scandal (he was dramatically incapacitated and rendered unable to speak just hours before he was to testify before Congress; whatever he knew or participated in went to the grave with him, which has been fodder for the conspiracy theorists ever since).
We know GBM is highly invasive because we can see it on brain studies, like MRI and CT. In the days before such modern imaging, brain surgeons tried doing lobectomies (removing an entire anatomic section of brain), and even hemispherectomies (removing fully half the brain!). Such radical therapy didn’t work however, and examination of brains removed at autopsy after such failed operations demonstrated why. GBM is a highly invasive disease that sends out tiny fronds of tissue to remote and distant parts of the brain. Even though we can’t see these fronds either grossly or on scans, we know they are there because after such radical operations, the tumors would recur on the other side of the head, making regrowth and subsequent death only a matter of time.
I often use the following analogy with my patients when discussing malignant brain tumors. Consider the brain itself to be a bucket of white paint. If the tumor is imagined to be red paint, one can see that even a single drop of the red paint admixed with the white will be impossible to remove once a little stirring occurs. This is the problem in treating brain cancer—remove 99.999% of the malignant cells, and the few remaining will eventually rise again to wreak havoc. This is why some brain cancer patients appear to be cured, even for long periods of time, only to succumb to a recurrence of their tumor.
Of course, the above is greatly simplified. Surgery is not the only treatment for primary brain tumors, or even the first-line treatment. Surgery kills the vast majority of cells by removing the greatest tumor burden. Chemotherapy and radiation therapy, or some combination of them, tries to remove the remainder. In general these kill only dividing cells however, and at any given moment only a fraction of the tumor cells are in the proper state of cell division to be affected by these potent drugs and radiation. This situation can be addressed by repeated courses of therapy—regular courses of therapy every week or month for some extended period of time. Each new course hopefully kills off more and more of the malignant cells, while not doing too much damage to the normal cells. Of course, the body’s normally rapidly dividing cells—hair, digestive tract—are killed with the tumor. This is the source of hair loss, nausea, diarrhea, etc.
Can brain cancer be prevented? The answer is yes and no. Some forms can almost certainly be watched for and prevented, such as hereditary cancers and those occurring after radiation to the head for some other reason. But for the most part, we don’t know why people get brain cancer and thus we don’t know how to prevent it. This includes cell phones by the way. Although the subject is somewhat controversial amongst the lay public, there does not appear to be any evidence to suggest that cell phones have increased the incidence of primary brain tumors.
There will be 70,000 new cases of primary brain tumors diagnosed in the US this year. 4,600 of these cases will be children (brain tumors are the most common solid cancers in children; leukemia is the most common cancer overall in children and also the leading cause of cancer related deaths in children and young adults). My own brother contracted leukemia in high school and died of complications from his treatment just after we graduated high school.
About 700,000 people are currently living with brain tumors in the US. The vast majority of these will not die of their disease.
About 14,000 people die of brain cancer each year.