FRIDAY, Dec. 10, 2004 (HealthDayNews) -- A new genetic test could one day spare many women diagnosed with breast cancer from the rigors of chemotherapy, a new study says.
But at least one cancer expert says more research is needed before the test is widely embraced.
The study of stored tissue samples from 447 patients showed that the test, which looked at 16 cancer-related genes, successfully identified women at very low risk of having their cancer recur after treatment with tamoxifen, a standard drug for the disease.
Dr. Soonmyung Paik, director of the division of pathology at the National Surgical Adjuvant Breast and Bowel Project, reported the findings Dec. 10 at the San Antonio Breast Cancer Symposium in San Antonio.
The test is potentially applicable to about 50 percent of women diagnosed with breast cancer, Paik said. They include women with cancers that are lymph-node-negative, meaning the cancer has not spread past the breast, and receptor-positive, meaning the tumor cells have receptors that make them grow when exposed to the hormone estrogen.
The study results indicate that half of those women, perhaps 25,000 each year, do not require the follow-up chemotherapy they now get, Paik said.
The test, which was developed with the help of the National Cancer Institute (NCI), is commercially available now, but is not widely used, he said. While the test "at this point is very expensive," medical economic analyses indicate that it might pay for itself through reduced treatment costs, Paik said.
A report on the findings will also appear in the Dec. 30 issue of the New England Journal of Medicine.
However, another cancer expert said widespread use of the test should await further studies of its effectiveness.
Dr. Robert C. Bast Jr., co-author of an accompanying editorial in the journal, is vice president for translational research at the University of Texas M.D. Anderson Cancer Center. As such, he's responsible for bringing procedures out of the laboratory into everyday practice.
One reason why more trials are needed, Bast said, is that none of the women in the new study were treated with a new generation of cancer drugs called aromatase inhibitors, which are starting to displace tamoxifen, he explained.
In fact, a study presented Dec. 8 at the San Antonio conference found the aromatase inhibitor anastrozole was significantly more effective than tamoxifen in increasing the number of women who remained free of cancer, lengthening the time before cancer recurred in many patients and reducing the incidence of cancer spreading, particularly to the other breast.
Bast said another reason to wait for more research on the genetic test is that the new study was "retrospective" -- it looked back at women who already had been treated with tamoxifen. Prospective studies, which begin when women are diagnosed, are needed "to confirm this finding in general," Bast said.
Bast said he's not using the genetic test in his practice. "I would await confirmational studies," he said. "If they are as strongly positive as this one, the test should go into wider use."
Such studies are being planned, said Sheila E. Taube, associate director of the cancer diagnosis program at NCI.
"NCI is working with clinical trials groups to develop a trial that will in fact test the recurrence score prospectively," Taube said. "The final design is not decided on yet, but it most likely will focus on the group about which we need the most information, women in the intermediate risk group."
For more on breast cancer and chemotherapy, visit the National Cancer Institute.