The study followed a relatively small group of breast cancer patients who were younger than 53 when diagnosed. The genetic researchers appeared to be able to predict which patients would be most likely to die from their cancer. The study did not address how best to treat breast cancer patients.
The results of this study have not been confirmed, but other studies on predicting tumor growth through genetic testing are underway.
Doctors currently predict whether breast cancer will spread based on factors such as the tumor’s size, how it looks under a microscope and the patient’s age, since breast cancer in younger women tends to be more aggressive. However, such criteria give only a rough prediction. To be safe, doctors provide chemotherapy to the vast majority of these women, despite side effects such as nausea, fatigue and hair loss. If doctors can determine how aggressive a tumor is through a genetic test, women with tumors that are unlikely to spread may be spared having to go through chemotherapy.
“The hope and the expectation is that we will be able to identify subsets of patients who require less aggressive therapy, or perhaps no therapy at all,” said Dr. Todd Golub, who directs cancer genomics research at the Whitehead/MIT Center for Genome Research in Cambridge, Mass, told The New York Times.
Using a test developed by the Netherlands Cancer Institute, the researchers tested the tumor cells of 295 women who had breast cancer. The Dutch team discovered 70 genes that, when turned on or off in a certain pattern, predict whether the cancer will spread and kill a patient.
In the group genetically defined as high-risk, half of them developed cancer elsewhere and 45 percent died within 10 years. In the low-risk group, 85 percent stayed free of recurrences and 95 percent survived. The high-risk patients were five times more likely to have their cancer spread.
The genetic test would put 61 percent of the women into the high-risk category, compared with 90 percent under standard American methods, the researchers found. Since high-risk cases are candidates for chemotherapy, the genetic test could reduce the number of women getting chemotherapy by a third.
The Dutch group plans to begin using the technique on breast cancer patients next year at the Netherlands Cancer Institute. It also plans to join with researchers at Massachusetts General Hospital in Boston to further test the results to satisfy U.S. government regulators.
Some 200,000 U.S. women are diagnosed with breast cancer and 40,000 die each year, according to the American Cancer Society.