For women with early-stage breast cancer, many surgeons would advise extensive removal of the lymph nodes under the armpits even though recent evidence shows this doesn’t improve survival or the odds of cancer recurring, a U.S. study found.Nearly half of breast cancer surgeons surveyed said they would recommend the procedure, known as axillary node dissection, despite modern guidelines that recommend against it.

Women have 20 to 40 lymph nodes under the armpits. When cancer surgeons remove an early-stage breast tumor, they also remove a few “sentinel lymph nodes,” so-called because they’re the first lymph nodes to which cancer cells are most likely to spread from the original tumor.

In the past, when sentinel nodes contained cancer cells, surgeons would routinely cut out most or all of the remaining nodes to prevent the cancer from spreading or recurring. But based on the most current evidence, the American Society of Clinical Oncology changed its guidelines in 2014 to say that women with one or two positive sentinel nodes who plan to have lumpectomy plus radiation don’t need axillary node surgery.

“Early breast cancers are unlikely to have involvement of multiple lymph nodes, so removing the sentinel nodes removes the bulk of the cancer in the lymph nodes,” said the new study’s lead author Dr. Monica Morrow, chief of the breast service at Memorial Sloan Kettering Cancer Center in New York City.

“Studies have shown that any remaining cancer in the nodes is treated with the radiation that is standard after (breast conserving surgery) and the drug therapy (chemotherapy and or hormone therapy) that is part of the management” of women with cancer in one or two sentinel nodes, Morrow said by email.

The study team surveyed 376 breast surgeons about how they would treat women with tumors that had advanced to one or two sentinel lymph nodes.

Forty-nine percent of the surgeons said they would definitely or probably perform an axillary node dissection if women had cancer in a single sentinel node. And 63 percent had the same approach when women had cancer cells in two sentinel nodes.

Surgeons who did a higher volume of breast cancer procedures were less likely to advise women with early-stage tumors to get all axillary nodes removed, researchers report in JAMA Oncology.

Axillary node dissection can lead to lingering problems, including a swollen arm, stiffness or trouble moving the arm or shoulder, and changes in sensation, such as pain or numbness.

The approach of not removing all the lymph nodes applies only to women don’t have suspicious lymph nodes to feel on physical exam, are planning treatment with lumpectomy and radiation, and have not received preoperative chemotherapy, Morrow said.

For these women, “if the surgeon says they are going to remove the sentinel nodes, look at them under the microscope during surgery and proceed directly to complete lymph node removal if any cancer cells are present, a second opinion about the need for this should be obtained from another surgeon,” Morrow advised.

One limitation of the study is that researchers only surveyed surgeons in the state of Georgia and the city of Los Angeles, and practice patterns might be different elsewhere, researchers acknowledge. It’s also unclear whether surgeons’ survey responses mirror what they would do in the operating room.

Even so, the results offer fresh evidence that new treatment strategies are not always immediately embraced, said Dr. Benjamin Anderson, author of an accompanying editorial and a professor of surgery and global health at the University of Washington in Seattle.

“Sometimes there is skepticism that the newest studies are correct,” Anderson said by email. “Other times surgeons may not be fully informed, especially when it relates to doing less rather than more.”

Long-term evidence suggests that advanced tumors with large amounts of cancer in the lymph nodes require surgical removal, because the amount of tumor may be more than radiation and drug treatment can control, Anderson said. The newest studies show that when the amount of disease in the nodes is minimal and microscopic, surgical removal is not necessary as long as radiation and drug treatments are being given.

“The cross-over point of when we can step away from surgical removal of cancer in the nodes is what we are studying today,” Anderson said. “The goal is to do less when it is safe to do so.”