A gene test used to guide treatment for early-stage breast cancer proved effective in enabling certain women to safely forgo chemotherapy, in a study that illustrates how genomic information is reshaping cancer care. Researchers said the findings provide validation for the test, called Oncotype DX, which is already in use helping women decide whether chemotherapy should be part of their treatment. The test provides a score based on a tumor’s genetic signature that describes the risk that the cancer will recur.
Oncotype DX analyzes 21 genes in the tumor to estimate a woman’s risk of the cancer coming back after surgery.
For patients who fell into the test’s low-risk category, 99 percent didn’t develop metastatic breast cancer five years after surgery, even though they didn’t have chemotherapy. The overall survival rate among this group was 98 percent, doctors reported in the New England Journal of Medicine.
“We knew these patients were going to do well, but we didn’t dream they would do this well,” said Joseph Sparano, associate chairman of medical oncology at Montefiore Medical Center and Albert Einstein College of Medicine in Bronx, N.Y., and lead author of the study.
Jennifer Litton, a breast medical oncologist at University of Texas MD Anderson Cancer Center in Houston, who wasn’t a researcher on the study, said she is eager to see results for patients in the midrange, where earlier data are ambiguous. “That’s the tougher conversation with patients,” she said. The current findings provide assurance for oncologists who already use the test to guide treatment of low-risk patients. “This is a group of patients that we are likely over-treating with chemotherapy,” Dr. Litton said. “Using this test we can spare these patients from chemotherapy.”
“This is very reassuring that the guidelines we’ve been following are right,” says Dr. Daniel Hayes, who co-directs the Breast Oncology Program at the University of Michigan and contributed to the current study. “It’s one more step forward to personalizing how we treat patients.”
But, for a large percentage of patients, the Oncotype DX test is still ambiguous, Hayes says. Nearly 70 percent of the patients in the study scored in the mid-range of the test and were considered a moderate risk for a relapse.
Hayes and his colleagues are now testing to see which of these patients benefit from chemotherapy. The results of that trial are due out in a few years.