The most common and deadly form of brain tumor is not one disease, but at least four subtypes, scientists at UNC-Chapel Hill and other institutions reported Tuesday.
Each type of tumor, called a glioblastoma, has distinct molecular features that possibly arise from different causes. Knowing that should help scientists develop targeted treatments.
Currently, glioblastomas are nearly always fatal, and the average survival after diagnosis is about a year. It is the form of brain cancer that killed Sen. Edward Kennedy last year, despite aggressive treatment that included surgery at Duke University Medical Center.
The UNC-CH team - participating in a National Institutes of Health effort to map the genetic structure of 20 cancer types - scoured a vast database to compare healthy human DNA against glioblastoma.
A surprising pattern emerged. While the brain tumors looked the same under a microscope, they showed remarkable differences when examined more closely at the molecular level. Some were missing parts of chromosomes; others had extra parts.
'A new era'
"This is really a quantum step," said Dr. David Neil Hayes, lead author and researcher at UNC Lineberger Comprehensive Cancer Center. "With genomics technology, we are really looking at a time and progress in science that's equivalent to some of the major advances such as the microscope. This is the dawn of a new era in the study of human disease."
The new frontier has been touted for years as personalized medicine - disease diagnoses and treatments gauged to a patient's unique genetic makeup. Already, doctors are making treatment decisions for some breast and other cancers based on the molecular construction of the tumors.
With glioblastomas, Hayes said, a similar approach is not far off, and he said new drugs in the pipeline have the potential to target one or another of the four tumor subtypes.
Patient groups welcomed the findings, which were published Tuesday in the journal Cancer Cell.
"This is a wonderful discovery," said Dianne Traynor, president of the Pediatric Brain Tumor Foundation in Asheville, which funds research and provides advocacy to patients and families. "This is very important, because it can be sparing to patients when we know the differences."
Traynor said some patients may opt to forgo treatment if they know it's ineffective on their type of tumor. Additionally, less medicine may work on tumors that do respond, sparing patients from toxic side effects.
The findings could also spur research into new drugs.
"This study will be highly relevant to patients in speeding up development of appropriate new therapies for their particular tumors," said David R. Hurwitz, chief science officer of the National Brain Tumor Society.
Hayes, the UNC-CH researcher, said the mapping effort for glioblastoma is just the start of a five-year mission to decode the molecular structures of cancer tumors. The program, called The Cancer Genome Atlas, involves dozens of research institutions, with UNC-CH working to decipher how the genes are expressed.
"TCGA is mobilizing the entire cancer community to find new strategies in detecting and treating cancer faster," NIH Director Dr. Francis Collins said in a prepared statement. "These findings are just a hint of what we expect to result from the comprehensive data generated by TCGA over the next few years."
Findings about ovarian cancer are expected to be reported next, Hayes said.
