5 questions about the brain cancer diagnosed in US Senator John McCain

US Senator John McCain. Photo / AP

By Laurie Mcginley

Glioblastoma, the cancer with which US Senator John McCain has been diagnosed, is a highly lethal malignancy that killed Senator Edward Kennedy and Beau Biden, the son of former Vice-President Joseph Biden. Here is what you need to know:

1 What is glioblastoma?

Glioblastoma is an aggressive cancer that is the most common of all malignant brain tumours. About 12,400 new cases are expected in 2017, according to the American Brain Tumour Association. The tumours arise from the brain's glial cells, which are cells that are wrapped around neurons throughout the central nervous system. Typically, said Matthias Holdhoff, associate professor of oncology at Sidney Kimmel Comprehensive Cancer Centre at Johns Hopkins University, "the tumours are considered not curable".

About 23,000 adults, more of them men than women, are diagnosed with various types of primary brain cancers a year, according to Cancer.net, a web site of the American Society of Clinical Oncology. Unlike most other cancers, brain tumours do not spread to other parts of the body. They kill by interfering with normal body function, depending on their location.

2 What are some symptoms of a glioblastoma?

Depending on the location of the tumour, a patient can have seizures, headaches, blurred vision and confusion.

3 How is it treated?

The first step is surgery to remove as much of the tumour as possible. But because the cancer has "extensions" that spread throughout the brain tissue, excising every bit of the malignancy is difficult, Holdhoff said.

After surgery, patients typically receive six weeks of oral chemotherapy and radiation. Sometimes that course of treatment is reduced to three weeks for older people. After that, most patients get chemotherapy several days a month for an additional six months.

The median survival time following that treatment is about 15 to 16 months, Holdhoff said. But that varies considerably: "It's not just a matter of the cancer but where it is and what it's doing to the patient," agreed Frederick Smith, a Washington, DC, oncologist.

Age can affect how long a person survives; in general, being young is better. Other key factors include how well a person was functioning before being diagnosed and the molecular characteristics of the tumour.

4 What about immunotherapy?

New treatments that unleash the immune system against malignancies can help patients with several kinds of cancer, including metastatic melanoma and lung and bladder cancers. But while there are many clinical trials testing immunotherapy for glioblastoma, so far the studies haven't shown a meaningful survival benefit, experts say.

5 What happened to Kennedy and Biden?

Kennedy disclosed his diagnosis in May 2008, three days after suffering a seizure. He underwent more than three hours of surgery shortly after that at Duke University. He died in August 2009. Biden, a former attorney-general for the state of Delaware, was diagnosed in 2013 and had surgery, radiation and chemotherapy before going back to work. He died in May 2015 at the age of 46.