Joseph "Beau" Biden's recent death from brain cancer at age 46 highlights the mysteries of this uncommon yet often lethal form of cancer.
It's not clear what type of brain cancer Biden had, but in 2013, he had a small lesion removed from his brain, according to The New York Times. Some politicians thought Biden, son of Vice President Joe Biden and former attorney general of Delaware, might be well enough to run for governor of Delaware in 2016, but his health declined in recent weeks, The New York Times reported. After spending a week at Walter Reed National Military Medical Center, Biden died Saturday (May 30).
Brain cancer is a rare type of cancer, accounting for only about 1.4 percent of all new cancer cases in the United States, according to the National Cancer Institute. Here are five facts about brain cancer:
There are many different types of brain tumors, and some types have low survival rates.
Brain tumors occur when cells in the brain grow abnormally (known as primary brain tumors), or when cancers spread from other parts of the body to the brain (known as metastatic brain tumors). The Johns Hopkins School of Medicine estimates that there are more than 120 types of primary brain tumors.
Some brain tumors are benign, meaning they are not made up of cancer cells. These tumors tend to grow slowly, and don't often spread to other parts of the brain or body, but they can still be dangerous because they may press on brain tissue as they grow, causing problems that can be disabling, according to the American Cancer Society.
Malignant brain tumors, in contrast, grow more quickly, and are more likely to be life-threatening, according to the National Cancer Institute. In 2015, there will be an estimated 22,850 new cases of malignant brain tumors, and 15,320 deaths due to malignant brain tumors, in the United States. About a third of patients with malignant brain tumors survive for at least five years after their diagnosis, the NCI says. [10 Things You Didn't Know About the Brain]
One particularly aggressive form of brain cancer is glioblastoma. Only about 6 percent of people with glioblastoma ages 45 to 54, and 4 percent of those ages 55 to 64, survive for at least five years after their diagnosis, according to the American Cancer Society.
But other types of brain tumors have better prognoses. More than 90 percent of people ages 20 to 44 who are diagnosed with a benign type of brain tumor called a meningioma, and 77 percent of those ages 45 to 54 who are diagnosed with this type of tumor, survive for at least five years.
The cause of brain cancer is usually unknown.
One of the mysteries of brain cancer is what causes the disease. Most people with brain cancer don't have any known risk factors for the disease, according to the NCI.
But there are a few factors known to increase the risk of brain cancer. One factor is exposure to a type of radiation called ionizing radiation, which is used to treat certain cancers, although the development of brain cancers from this type of radiation is rare, according to the ACS. Ionizing radiation is also released during nuclear explosions.
In rare cases, brain cancers can run in families, meaning a genetic mutation is linked with the cancer.
Brain tumors can occur at any age.
Brain tumors can occur in both children and adults. Such tumors are the second most common form of cancer in childhood, after leukemia, according to The Children's Hospital of Philadelphia.
In adults, meningiomas and gliomas (the latter of which form from a type of brain cell called glial cells) are the most common brain tumors in adults, according to the National Institutes of Health.
Headaches aren't the only symptom of brain cancer.
Headaches that get worse over time are a common symptom of brain tumors. But brain tumors can cause a number of other symptoms, including blurred vision, problems with balance, seizures and personality changes, according to the ACS.
It's important to note that these symptoms are usually not caused by a brain tumor, but if you experience these symptoms, you should speak with your doctor so that he or she can determine the cause, the NCI says.
Cellphones aren't proven to cause brain cancer.
Most studies have not found a link between cellphone use and the risk of brain tumors.
Cellphones emit radio-frequency energy, which can be absorbed by tissues, according to the NCI. But so far, the only known biological effect of this energy, which is also emitted by microwave ovens, is a tiny rise in temperature, the NCI says.
Unlike the ionizing radiation, radio-frequency energy is not known to damage DNA. (Damage to DNA is considered a necessary step to cause cancer, the NCI says.)
In addition, between 1987 and 2007 — a period when cellphone use rose rapidly — there was no increase in diagnoses of brain cancer in the United States, the NCI says.