New Screens May Find Early Prostate, Ovarian Cancer
Studies give early tumor detection a boost
TUESDAY, April 2, 2002 (HealthDayNews) -- When it comes to detecting and treating cancer, the old saying "better late than never" generally doesn't apply.
Fortunately, two studies in tomorrow's issue of the Journal of the American Medical Association offer hope for early warnings on two major killers: ovarian cancer and prostate cancer. Together, these diseases account for more than 50,000 deaths a year in the United States alone.
In the first study, Dr. Arul Chinnaiyan and his colleagues at the University of Michigan used "DNA chip" technology to find genes that become overactive in prostate cancer. The disease is the most common cancer in men, diagnosed in 180,000 Americans each year. Although it can be cured with surgery and other therapies, 40,000 in this country die of prostate cancer annually.
Chinnaiyan's group, which earlier identified two genes that may help doctors predict the aggressiveness of prostate tumors, found a third gene, called AMACR, which is elevated exclusively in a cancerous gland.
"It's probably the best marker that we've seen that distinguishes prostate cancer from benign prostate [enlargement]," Chinnaiyan says. "It's very specific for cancer, and we think it has a high potential for being a diagnostic marker."
AMACR produces an enzyme, a-methylacyl-CoA racemase that helps cells break down fatty acid molecules. Chinnaiyan says it's not clear exactly what role the enzyme plays in prostate cancer, although tumors usually require more fatty acid metabolism to keep up with their frenetic growth.
Chinnaiyan says AMACR, which is easy to test for, could help doctors facing a fuzzy prostate biopsy. Such ambiguity occurs in about 15 percent to 20 percent of samples, he says.
However, the Michigan researchers also hope the gene might be useful as a screening test. If so, it would have an advantage over the current prostate screening exam, prostate-specific antigen (PSA). This test picks up elevations in a blood protein shed by prostate tumors. Unfortunately, it's produced by benignly enlarged glands, too, leading to much unnecessary treatment.
AMACR, on the other hand, appears only to be elevated in the presence of cancer, so a positive result would mean a tumor. The question, Chinnaiyan says, is whether it can be detected in blood. "We're starting to look in serum to see if it's shed," he adds.
The alphabet soup combination of PSA and AMACR has "a lot of potential" as a screening test, says Dr. Mark Rubin, a co-author of the paper. In addition, the researchers have been finding other genes that in concert could be able to greatly enhance the ability of doctors to find and treat prostate cancer.
Dr. Jonathan W. Simons, director of the Winship Cancer Institute at Emory University in Atlanta, calls the latest discovery "an important result."
"Everybody knows the PSA test is incredibly helpful, but since it received [Food and Drug Administration] approval we've been struggling to improve on it," Simons says. "I can't wait to use [the new gene test] in my patients."
The new test is not yet on the market, although Chinnaiyan and his colleagues are seeking to patent AMACR and the other prostate cancer genes they uncover.
In the second study, a team led by Harvard Medical School oncologist Samuel Mok found a protein that appears to be sharply elevated in women with ovarian cancer.
Mok's group looked for concentrations of the protein osteopontin in 144 women undergoing treatment for pelvic tumors, some benign, some cancerous. Osteopontin earned its name because it plays a role in the formation and erosion of bone, but it has also been found in many other tissues throughout the body.
Osteopontin levels were roughly four times higher, on average, in women with ovarian cancer than in those without the disease, the researchers say. They were also elevated, though somewhat less so, in ovarian cancer patients compared to women with benign tumors or to those with other forms of reproductive cancers.
Ovarian cancer claims 15,000 lives a year in this country, largely because it is usually detected in later stages. The five-year survival rate for the tumors is 95 percent when found early, a figure that drops to just 30 percent when the cancer is far advanced upon discovery.
What To Do: To find out more about ovarian cancer, visit the National Ovarian Cancer Coalition or the National Library of Medicine. For more on prostate cancer, try the University of Michigan or the Prostate Cancer Research Institute.