Study finds many early breast cancer patients can skip chemo; gene test helps ID which ones
Many women with early-stage breast cancer can skip chemotherapy without hurting their odds of beating the disease — good news from a major study that shows the value of a gene-activity test to gauge each patient's risk.
The test accurately identified a group of women whose cancers are so likely to respond to hormone-blocking drugs that adding chemo would do little if any good while exposing them to side effects and other health risks. In the study, women who skipped chemo based on the test had less than a 1 per cent chance of cancer recurring far away, such as the liver or lungs, within the next five years.
"You can't do better than that," said the study leader, Dr. Joseph Sparano of Montefiore Medical centre in New York.
An independent expert, Dr. Clifford Hudis of New York's Memorial Sloan Kettering Cancer centre, 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 was sponsored by the National Cancer Institute. Results were published online on Monday by the New England Journal of Medicine and discussed at the European Cancer Congress in Vienna.
The study involved the most common type of breast cancer — early stage, without spread to lymph nodes; hormone-positive, meaning the tumor's growth is fuelled by aestrogen or progesterone; and not the type that the drug Herceptin targets. Each year, more than 100,000 women in the United States alone are diagnosed with this.
The usual treatment is surgery followed by years of a hormone-blocking drug. But many women also are urged to have chemo, to help kill any stray cancer cells that may have spread beyond the breast and could seed new cancer later. Doctors know that most of these women don't need chemo, but there are no great ways to tell who can safely skip it.
A California company, Genomic Health Inc., has sold a test called Oncotype DX since 2004 to help gauge this risk. The test measures the activity of genes that control cell growth, and others that indicate a likely response to hormone therapy treatment.
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 per cent were classified as low risk, 67 per cent as intermediate and 17 per cent 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 chemo. Results on these groups are not yet ready — the study is continuing.