Women with early stage breast cancer that is hormone receptor-positive, HER2-negative, and lymph node-negative, but who — based on a 21-gene expression assay — are thought to be at intermediate risk of recurrence have similar outcomes regardless of whether they received chemotherapy after surgery or not, a new study at The University of Texas MD Anderson Cancer reports.

While the study needs further validation, its results suggest that women at intermediate recurrence risk may skip chemotherapy as standard of care.

The retrospective and single-institution study, “Outcomes in patients with early-stage breast cancer who underwent a 21-gene expression assay,” was published in the journal Cancer.

Women with early stage breast cancer have long been treated with aggressive therapies, with many stage 1 and 2 cancer patients receiving chemotherapy. But researchers are starting to understand that for this patient population, less is more.

“Through years of research discoveries, it became clear that we were over-treating many women with breast cancer, especially those with early-stage disease. In addition to chemotherapy’s obvious side effects, there were also long-term complications for these women as survivors,” Carlos H. Barcenas, MD, assistant professor, Breast Medical Oncology, the study’s corresponding author, said in a press release.

In the Phase 3 clinical trial, named TAILORx (NCT00310180), researchers found that women with hormone-receptor positive, HER2-negative, and lymph node-negative early stage breast cancer with a low recurrence score (0-10) in the 21-gene expression assay could skip chemotherapy. Those who were given chemotherapy had outcomes similar to those who were not.

The findings led to a dramatic change in the standard of care for women with low recurrence scores, but whether women with intermediate risk (those with a score of 11-25 in the test) benefited from chemotherapy was still largely unknown. The Phase 3 study, which began in 2006 and involves almost 11,250 patients throughout the U.S., Europe, Canada and elsewhere, is expected to finish in December.

“This study evolved out of my patients’ frustration that I could not provide a definitive answer to their paramount question: ‘Do I need chemotherapy?’ As we wait for the TAILORx findings, we decided to look at MD Anderson’s own experience to glean insight on how best to care for these women with an intermediate risk recurrence score,” Barcenas said.

The retrospective study included 1,424 breast cancer patients treated at the MD Anderson Cancer Center between 2005 and 2011. All were hormone positive, HER2 negative, and lymph node negative and received surgery as primary treatment.

Using the 21-gene expression assay with the same cutoff scores of the TAILORx trial, the researchers identified 297 patients at low risk of recurrence (score 0-10), 894 at intermediate risk (score 11-25) and 233 patients at high risk (score greater than 25). Among them, 1.7%, 15%, and 73.4%, respectively, received chemotherapy after surgery.

After a median follow-up of 58 months, results showed that intermediate risk patients had a five-year invasive disease-free survival (IDFS) of 92.6%, regardless of whether they received chemotherapy or not.

The five-year IDFS rates were 89% and 93% among those who received chemotherapy and those who did not, respectively.

Adding to the evidence that chemotherapy does not benefit this patient population, the researchers also found that the five-year overall survival was 98% in both groups.

But the team highlights that their study had limitations, and they are waiting for an update on the TAILORx trial to validate their findings.

“Our research is likely the most comprehensive data we will have about this patient population until the international randomized trial is published,” said Barcenas. “Hopefully our findings will serve as a discussion point between physicians and patients as they are making critical decisions regarding a woman’s breast cancer care.”