New test aids breast cancer treatment, studies show

Genetic analysis predicts likelihood of recurrence

December 11, 2004|By David Kohn | David Kohn,SUN STAFF

A new genetic test accurately predicts which women will have a greater chance of breast cancer recurrence, according to studies that hold out hope of increasing survival rates among high-risk patients while helping others avoid agonizing chemotherapy.

"The results are quite striking," said one of the researchers, JoAnne Zujewski, director of breast cancer therapeutics in the Clinical Investigations Branch of the National Cancer Institute.

The technique was the subject of three new studies, which were released yesterday and Thursday at the San Antonio Breast Cancer Symposium. One of the three was published online in the New England Journal of Medicine.

Known as Oncotype DX, the test looks at 21 genes that influence the behavior of breast cancer cells - how aggressive they are and how quickly they grow. The test, introduced this year, was developed by Genomic Health Inc., a California biotech company.

"The test will have a powerful clinical impact," said Dr. Steven Shak, one of the researchers. Shak is the chief medical officer of Genomic.

The studies focused on women who had a relatively low-risk type of breast cancer, in which cancer cells contained estrogen receptors and had not spread to the lymph nodes. About a third of the 200,000 American women diagnosed with breast cancer every year have this node-negative, estrogen receptor-positive variant. It is generally treatable with surgery and drugs that slow cancer growth by blocking estrogen.

Once the cancer is under control, many women undergo chemotherapy to ensure that the disease doesn't return. Researchers have long known that most chemotherapy patients won't suffer relapses anyway and don't need the treatment, which can cause hair loss, nausea, fatigue and immune system weakness. Although only 20 percent of patients in the node-negative group have recurrences, more than 80 percent go through chemotherapy.

But until now it has been difficult to pinpoint which women would benefit most from chemotherapy.

The studies looked at breast cancer tissue taken from women who had been diagnosed over a decade ago. The tissue, which had been saved, was analyzed with the Oncotype DX technique. Researchers found the test could predict in most cases whether the cancer recurred.

The study in the New England Journal of Medicine looked at 668 tissue samples, and divided them into low-, intermediate- and high-risk groups: About half were in the low-risk group, and the other two categories had about a quarter each.

Researchers then looked at recurrence rates 10 years later and found the test's predictions were accurate. Seven percent in the low-risk group had recurrences, compared with 14 percent in the medium group and 30 percent of the high-risk group.

Two of the studies were part of the National Surgical Adjuvant Breast and Bowel Project, a long-running series of studies funded largely by the National Cancer Institute, a part of the National Institutes of Health. The third study was done by researchers at Kaiser Permanente, a large national health insurance plan. All three received funding from Genomic Health.

But some experts cautioned that current breast cancer tests provided some of the same information as the new technique.

"It looks at some of the same things we already look at," said Dr. Deborah Armstrong, an assistant professor of oncology at the Johns Hopkins School of Medicine. She pointed out that several routinely used tests analyze levels of cancer-related proteins. These proteins are produced by some of the 21 genes targeted by the newer test; in essence, the older tests provide similar information about disease activity, she said.

Others argued that the new technique must be tested more thoroughly. "This is very encouraging work, but we want to be sure that it is right," said Robert Bast, a cancer specialist at the University of Texas' MD Anderson Cancer Center.

Bast wrote an editorial accompanying the study that appeared in the New England Journal of Medicine. He noted that a study published last year had found that Oncotype DX tests did not predict which women would have recurrences.

He worried that people might come to rely on the test too much before it has been proven. If it turned out not to work, the test could potentially endanger lives: Patients labeled as "low-risk" might decide to forgo chemotherapy and end up with cancer.

Genomic hopes to expand the technique to include other types of cancer.

"This idea of individual medicine should be widely applied," Shak said.

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