NEW YORK
(AP) — A new experimental test may someday help doctors with one of the most
vexing problems in cancer therapy: identifying which prostate cancer patients
need aggressive treatment.
Currently, once prostate cancer is diagnosed, doctors have
no reliable way to know which cases are life-threatening. Most are not. So
doctors have a difficult time determining whether they should monitor the
cancers to see if they progress or recommend immediate treatment, such as
surgery or radiation. Both treatments can cause problems, such as incontinence
and impotence.
The dilemma results in overtreatment, such that about 48 men
are treated for every life saved, says Dr. Ronald DePinho of the Dana-Farber Cancer
Center in Boston.
But DePinho and colleagues have created a test they say
might help doctors identify dangerous tumors more accurately than is possible
now. In results published online Wednesday by the journal Nature, the
scientists showed an improvement in accuracy to 91 percent from 84 percent.
When applied to prostate cancer samples, the gene test
indicates “how this particular cancer is wired to behave,” DePinho
said.
Drawing on research in mice, DePinho and colleagues
identified four genes whose combined activity within cancers appears to drive
prostate tumors toward being lethal. The genes are involved in processes like
growth and ability to invade other tissues.
Then the researchers tested whether the combined activity of
those genes also predicted cancer outcome in men, with a series of tests in
human tumor samples.
In the largest test, they looked at 405 tumor specimens from
men who’d been diagnosed between 1983 and 2004. Thirty-eight cases turned out
to be lethal. Researchers looked for the chemical signatures of gene activity
in the samples and tested how accurately that could classify tumors as lethal
or not.
By itself, the gene test performed about as well as a
combination of current indicators: age at diagnosis, indications of tumor
spread and a “Gleason score” that assesses the appearance of tumor
cells under a microscope. That standard approach was accurate 84 percent of the
time in the study.
But accuracy rose to 91 percent when researchers combined that
approach with the gene test. The combination “robustly predicted which men
were going to die of the disease,” DePinho said.
The rights to develop the test have been licensed to a
company that DePinho co-founded and in which he holds a financial interest.
Experts not connected with the study praised the work but
said more research on the gene test is needed.
“It’s early still, but it’s pretty exciting,” said
Dr. Eric Klein of the Cleveland Clinic. “This is a step in the right
direction, without question.”
Dr. Angelo De Marzo, a professor of pathology, oncology and
urology at the Johns Hopkins School of Medicine in Baltimore, called it “extremely
interesting, promising, amazing work.”
It will take more research to see whether the gene test
really could help doctors make treatment recommendations with more confidence
than they can now, and in what situations, he said. The test might prove useful
when prostate cancer is diagnosed from biopsy samples, or in deciding on
further treatment after a man’s prostate has been removed, he said.
De Marzo noted that some prostate cancer researchers are
meeting this weekend, and “I have a feeling there’s going to be a ton of
buzz about this at that meeting. I think people are going to be very excited.”
