Genetic test shows which breast cancer patients can skip chemotherapy

A genetic test may be able to determine whether women with early-stage breast cancer can skip chemotherapy treatment and beat the disease with hormone therapy, according to a study released Monday.

By looking at the activity of 21 genes in the cancer tumor, the genetic test was able to accurately decipher whether women with early-stage breast cancer can take hormone-blocking drugs for treatment and forgo the chemotherapy that would often be prescribed along with it. Chemotherapy often has unpleasant side effects that include fatigue, hair loss, nausea and loss of appetite.

The study, which was published in the New England Journal of Medicine, included more than 10,000 women between the ages of 18 and 75. Researchers found that women who tested below a certain genetic risk level for recurrence were able to bypass chemotherapy and still had less than a 1 percent chance of the cancer returning in another part of the body within five years.

"You can't do better than that," said the study’s lead author, Dr. Joseph Sparano of Montefiore Medical Center in New York.

An independent expert, Dr. Clifford Hudis of New York's Memorial Sloan Kettering Cancer Center, agreed.

"There is really no chance that chemotherapy could make that number better," he said. Using the gene test "lets us focus our chemotherapy more on the higher risk patients who do benefit" and spare others the ordeal.

The study, which was sponsored by the National Cancer Institute at the National Institutes of Health (NIH), was led by the ECOG-ACRIN Cancer Research Group in Philadelphia and Genomic Health, the Redwood City, California-based diagnostic testing company that makes the genetic test. The researchers presented their findings Monday at the biennial European Cancer Congress in Vienna.

The study involved an early-stage breast cancer that hasn’t yet spread to the lymph nodes and is responsive to the hormones estrogen and progesterone. This is the most common type of breast cancer among women, affecting more than 100,000 each year.

Normally, doctors would treat this type of breast cancer with surgery and hormone-blocking treatments, but they might also prescribe chemotherapy in case any cancer cells have spread to other parts of the body. Most women don't need chemotherapy, but there haven’t been reliable ways to tell who can safely skip the treatment.

Genomic Health’s genetic test, called the Oncoytpe DX, has been available since 2004, and works to measure the activity of certain genes that control cell growth as well as how responsive someone is to hormone therapy.

Past studies have looked at how women classified as low, intermediate or high risk by the test have fared. The new study is the first to assign women treatments based on their scores and track recurrence rates.

Of the 10,253 women in the study, 16 percent were classified as low risk, 67 percent as intermediate and 17 percent as high risk for recurrence by the test. The high-risk group was given chemotherapy and hormone-blocking drugs. Women in the middle group were randomly assigned to get hormone therapy alone or to add chemotherapy. Results on these groups are not yet ready, as the study is continuing.

But independent monitors recommended the results on the low-risk group be released, because it was clear that adding chemo would not improve their fate.

After five years, about 99 percent had not relapsed, and 98 percent were alive. About 94 percent were free of any invasive cancer, including new cancers at other sites or in the opposite breast.

"These patients who had low risk scores by Oncotype [the genetic test] did extraordinarily well at five years," said Dr. Hope Rugo, a breast cancer specialist at the University of California, San Francisco, with no role in the study. "There is no chance that for these patients, that chemotherapy would have any benefit."

Al Jazeera with wire services