The most common form of malignant brain cancer in adults is actually a set of four different pathologies, according to a study published Tuesday that could lead to more targeted treatment.
In identifying the separate subtypes of glioblastoma multiforme (GBM) brain tumors, the US research team found that each one may form in different types of cells and thus require separate therapies.
Most patients who develop GBM, which spreads rapidly to other parts of the brain and is challenging to treat, die within about 14 months after they are diagnosed.
Three of every 100,000 Americans have been diagnosed with the disease in recent years -- the highest incidence rate for malignant brain tumors. Among its most famous victims was the late senator Ted Kennedy, who died in August.
"We discovered a bundle of events that unequivocally occur almost exclusively within a subtype," lead author Neil Hayes of the University of North Carolina at Chapel Hill said in a statement.
"These are critical events in the history of the tumor's development and spread, and evidence is increasing that they may relate to the initial formation of the tumors."
This finding could help understand which types of cells undergo changes that are ultimately responsible for initial cancer formation, key to crafting targeted and effective treatment regimens.
Each subtype reacted differently to aggressive chemotherapy and radiation, the researchers found, which would mean that certain classes of drugs would work for some subtypes of brain tumors and not others.
Patients with one GBM subtype treated with aggressive chemotherapy and radiation seemed to be affected at a rate about 50 percent slower than those treated with less aggressive therapy.
This effect appeared less prominently in two of the subtypes and not at all in the fourth subtype.
For their study published in the journal Cancer Cell, the researchers analyzed patient samples as part of the Cancer Genome Atlas Research Network, a government-funded project launched in 2006 to map all DNA activity in different types of cancers.
"These findings demonstrate the power of using a cancer's genome to unravel the molecular changes that occur in the various cancer types targeted by TCGA," said Eric Green, director of the National Human Genome Research Institute, which is part of the National Institutes of Health.
"I'm optimistic that this type of knowledge will someday lead to improved personalized therapies and care for cancer patients."