Genetic Makeup of Tumors More Complex Than Thought
New Research Shows ‘Personalized’ Treatment for Cancer Not So ‘Simple’
March 8, 2012 -- A small study that shows a surprising complexity of genetic changes within a single tumor has far-reaching implications for the march toward personalized cancer therapy, according to researchers.
A single biopsy from a tumor might not be sufficient to give a full picture of its genetic landscape, a team from the United Kingdom reports.
When the researchers examined 10 biopsies taken from a single kidney cancer tumor, they found "an extraordinary amount of diversity" in the genetic changes that had taken place in different parts of the tumor.
"There were more differences between biopsies from the same tumor at the genetic level than there were similarities," said researcher Charles Swanton, MD, PhD, from the Cancer Research UK, London Institute, and the University College London, United Kingdom.
The findings, published in the New England Journal of Medicine, were highlighted at a London news conference organized by Cancer Research UK, which funded the study.
The team also found differences in genetic changes between the primary tumor and places in the body where the cancer spread. Similar findings have been documented by other research groups.
But it is the extent of the genetic changes that is surprising, the researchers note.
The findings have far-reaching implications for the efforts currently being directed toward personalized cancer therapy, in which therapy is targeted at genetic changes identified in tumor tissue. Swanton cautioned that "if you take only one biopsy, you could be misled clinically."
"I don't want to rain on anyone's parade, but the whole situation is far more complex than we could have imagined," he said.
"The simple view of directing therapy on the basis of genetic tumor markers is probably too simple," agrees Dan Longo, MD, deputy editor of the New England Journal of Medicine, in an accompanying editorial.
"A whole new world has been anticipated in which patients will undergo a needle biopsy of a tumor in an outpatient clinic, and a little while later, an active treatment will be devised for each patient on the basis of the distinctive genetic characteristics of the tumor," Longo writes.
However, a serious flaw in this imagined future of cancer treatment is the underestimation of genetic diversity within a tumor, he notes.