New test can help patients avoid unnecessary breast cancer treatment‚ including chemo

Many women with breast cancer can be subjected to grueling rounds of chemotherapy, radiation and medication after having a tumor removed. A new test could help women with a low-risk of cancer recurrence avoid those unnecessary additional treatments without risking their survival.

The test, called MammaPrint, examines the genetic makeup of a tumor to determine how aggressive it is likely to be. By identifying tumors that aren’t likely to spread, doctors and patients can minimize disruption caused by further treatment if the patient’s life isn’t at risk from the cancer.

“By using MammaPrint to identify a subset of patients who have excellent breast cancer-specific survival at 20 years with limited endocrine therapy treatment post-surgery, we can provide physicians and their patients with more options for better treatment and management of the disease,” said Dr. William Audeh, chief medical officer of Agendia, which holds the license for MammaPrint.

“For some women, endocrine therapy can be more difficult than chemotherapy and nearly 50 percent of patients are unable to complete their treatment, so identifying those women who could do very well with limited or no treatment is important.”

The genomic test examines 70 genes in a tumor, to help identify those that contribute to a tumor’s growth. Data from the study, which was published Thursday in JAMA Oncology, along with data from other recent studies, suggests about 20 to 25 percent of breast cancer tumors are low-risk enough not to require further treatment after surgery.

"We can tell [these] women that they are highly unlikely to die of their cancers and do not need aggressive treatment," Dr. Laura Esserman of the University of California, San Francisco, told NPR.

Esserman, along with Swedish colleagues, examined breast tissue samples from a large Swedish trial that began in 1976. Some of those women had been given tamoxifen, a drug that surpresses tumor formation, while some had radiation or received no further treatment. Of the 98 samples classified as ultra low-risk, 97 percent of women who’d taken tamoxifen survived at least 20 years. Ninety-four percent who did not take the drug also survived at least as long.

"There are breast cancers that pose little or no systemic risk," Esserman told Science Daily. "Women who have a tumor that is classified as ultralow risk by 70-gene signature can be reassured that their long-term outcome is expected to be excellent, with or without endocrine therapy.”

This story was originally published June 29, 2017 at 4:48 PM with the headline "New test can help patients avoid unnecessary breast cancer treatment‚ including chemo."