New test may better predict breast cancer return

A first-of-its-kind genetic test will soon be available to help women with breast cancer make one of their most crucial decisions: whether to undergo the rigors of chemotherapy.

Genomic Health Inc., a Silicon Valley biotech company, said it has identified nearly two dozen genes that, taken together, can predict with a high degree of accuracy the likelihood that tumors will return in women whose breast cancer was caught at an early stage.

Currently, doctors predict the chances of a relapse in pretty much the same way they have been doing it for almost a century: by looking at the patient's age, the size of the tumor, and the tumor's aggressiveness.

If the chances of recurrence are seen as very low based on the gene test, a woman may opt to not endure the vomiting, hair loss and high cost of chemo. But if the odds of the cancer coming back are high, she may view chemo as the difference between life and death.

"For the women in that highest group, it makes their decision so much easier," said Dr. Melody Cobleigh, a breast cancer researcher at Rush-Presbyterian-St. Lukes Medical Center in Chicago. "For women in the lowest group, they'll still agonize."

The biotechnology company's research -- done with the National Surgical Adjuvant Breast and Bowel Project -- was outlined Thursday at a breast cancer conference in San Antonio.

Chief executive Randy Scott said his company plans to make the test available to newly diagnosed cancer patients in early 2004.

Other genetic tests for predicting the chances of a relapse have been developed, but this would be the first to move beyond the experimental stage and reach the market.

The genetic test was developed by analyzing tumor samples from nearly 700 women involved in a 1980s cancer study. Genomic Health used its findings to create a point system to express escalating chances of recurrence within 10 years.

The sample group included women from their 30s to their 70s. All had early-stage breast cancer that had not spread to other parts of the body, and all had been treated for at least five years with tamoxifen, a drug that slows or stops the growth of new breast cancer cells.

Genomic Health found that just over half of the women in its sample group fell into the low-risk category. Their average recurrence rate was about 7 percent after surgery to remove the tumor, followed by tamoxifen.

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At the other end of the scale, 27 percent of the sample were determined to be at high risk of recurrence. About three in every 10 of these patients developed new breast cancer within 10 years of treatment.

In the intermediate-risk group, the 10-year recurrence rate averaged about 14 percent.

The error rate in each of the three categories was plus or minus 2 to 3 percentage points, said Dr. Steven Shak, Genomic Health's chief medical officer.