Prostate tumors with a distinctive four-gene "signature" are far more lethal than others, laying the groundwork for a test to predict which tumors need aggressive treatment, US researchers said on February 02. Tests of this four-gene signature method alone accurately identified 83 percent of deadly prostate tumors from tissue samples taken in a national health study.
When they combined this method with a standard test of a prostate tumour's aggressiveness, the team accurately identified more than 90 percent of tumours that later killed patients.
"This would have 92 percent accuracy relative to what we currently have, which is at best 75 percent accuracy," said Dr. Ronald DePinho of Dana-Farber's Belfer Institute for Applied Cancer Science in Massachusetts.
"There is no question this will influence the practical management of these cases," DePinho, whose study appears in the journal Nature, said in telephone interview.
He said such a test would spare many men from unnecessary treatment for cancers that might never have killed them.
"The vast majority of prostate cancers would not become life-threatening, even if left untreated. But because we can't accurately forecast which are likely to spread and which aren't, there is a tendency to unnecessarily subject many men to draconian interventions," he said in a statement.
Currently, he said, about 48 men must be treated for prostate cancer to save one life, and the main forms of prostate cancer treatment - surgery and radiation therapy - can cause impotence and incontinence.
To find genes that drive the aggressiveness of prostate tumours, DePinho said, his team "ping-ponged" between mouse and human studies.
They started out with mice that lack a working copy of the Pten gene, which is involved with cell growth. These mice develop tumours, but the tumours do not spread. They looked to see what genes kept those tumours from spreading and found a gene known as Smad4 that acts as a brake to cancer growth.