The majority of women with the most common type of early-stage breast cancer can safely skip chemotherapy after surgery, according to a highly anticipated new report. The results, released Sunday, are expected to accelerate the decline in chemotherapy for the disease.

“We have been waiting for these results for years,” said Allison Kurian, an oncologist at Stanford University who was not involved in the trial. “They are going to change treatment and remove uncertainty for women making decisions.”

The findings came from the largest breast cancer treatment trial ever conducted and showed that most patients who have an intermediate risk of a cancer recurrence — a group that numbers 65,000 women a year in the United States — can avoid chemotherapy and its often debilitating side effects.

The same decade-long study had previously confirmed that patients at low risk, as determined by a genomic test of their tumors, can skip chemotherapy.

The two groups taken together account for about 70 percent of women diagnosed with the most common type of breast cancer. That means more than 85,000 women a year can safely forgo chemotherapy.

The cancer in question is driven by hormones, has not spread to the lymph nodes and does not contain a protein called HER2.

The results came from a federally sponsored trial called ­TAILORx, which was designed to help doctors more precisely tailor treatments for early-stage breast cancer. Since 2006, the trial has enrolled more than 10,000 women in the United States and five other countries diagnosed with early-stage breast cancer and followed their progress through post-surgery treatment.

The patients’ tumors were analyzed using a test called Oncotype DX, which examines the activity of 21 genes to predict the risk of a recurrence over 10 years. Previous studies had made clear that women with low scores could skip chemotherapy and that those with high scores should get it.

The big outstanding question was: What should women with midrange scores get? Such patients have been in “the gray zone, and we haven’t known what to tell them,” Kurian said.

To find the answer, researchers randomly assigned more than 6,700 women with intermediate scores — 11 to 25 — to two groups. After surgery, one group got endocrine therapy only, while the other was treated with endocrine therapy plus chemotherapy. After years of follow-up, the data showed that most patients who did not get chemotherapy fared as well as those who did.

Women age 50 or younger were the notable exception. Those with recurrence scores of 16 and above got a “substantial” benefit from chemotherapy and should consider it, said lead author Joseph Sparano, associate director for clinical research at the Albert Einstein Cancer Center and an oncologist at Montefiore Medical Center in New York.

The trial results are the latest piece of the puzzle on how to treat early-stage breast cancer.

Most patients with the disease have a high survival rate, but their prognoses worsen drastically if their cancer returns in other parts of the body. Because of that, many women with early-stage cancer used to be urged to get chemotherapy in hopes of preventing any spread.

In recent years, however, as many doctors concluded that women with early-stage cancer were being overtreated, they have reduced their use of chemotherapy, which can cause nausea, fatigue and, in rare cases, more serious complications such as leukemia and heart failure.

James Doroshow, director of the cancer treatment and diagnosis division at the National Cancer Institute, which was the primary sponsor of the study, expects treatment guidelines to change quickly based on the findings.

He added that it was important the federal government funded the study because the pharmaceutical industry has little interest in sponsoring trials that result in a reduction of treatment.

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