A new study of women with early stage breast cancer finds that surgeons no longer universally remove most of the lymph nodes in the underarm area when a biopsy of the nearby lymph nodes shows cancer. This is a major change in breast cancer management. The study, which evaluated data from 2.7 million US breast cancer cases, was published by the Journal of the American College of Surgeons (2015; doi:10.1016/j.jamcollsurg.2015.02.035).

Until now, it was unclear to what extent surgeons were following the recommendations of a landmark clinical trial published more than 4 years ago, known as the American College of Surgeons Oncology Group Z0011, or ACOSOG Z-11, trial.

Those researchers reported that most early stage breast cancer patients with tumor in their sentinel lymph node (the first draining node) who undergo lumpectomy do not benefit from surgical removal of the remaining lymph nodes in the underarm area (completion axillary lymph node dissection [ALND]). That study found no difference in cancer recurrence and 5-year survival between patients who underwent ALND and those who did not but were monitored for recurrences.

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The new study found a dramatic increase in the proportion of lumpectomy patients who underwent only a sentinel lymph node biopsy (SNB) without an ALND after discovery of cancerous sentinel nodes.

According to the study authors, the SNB-alone rate more than doubled, from 23% in 2009—before publication of the first results of the ACOSOG Z-11 trial in September 2010—to 56% in 2011, the first year after publication.

“As far as I know, our study is the first to show that the findings from the ACOSOG Z-11 trial have changed clinical practice for breast cancer patients nationwide,” said lead author Katharine Yao, MD, FACS, director of the Breast Surgical Program at NorthShore University HealthSystem, Evanston, Illinois, and clinical associate professor of surgery at the University of Chicago Pritzker School of Medicine. “The Z-11 trial has had a huge impact because of the lower risks for patients who undergo SNB alone.”

Removal of small numbers of lymph nodes in SNB alone, according to Yao, greatly lowers the lifetime risk of developing the often disabling complication of lymphedema. This buildup of lymph fluid under the skin results in swelling and sometimes pain.

From the 2.72 million breast cancer cases diagnosed between 1998 and 2011 that were examined, the investigators found that 74,309 patients met the Z-11 trial’s eligibility criteria for having SNB alone.

Statistical analyses revealed that lumpectomy patients were more likely to undergo ALND if they had any of the following characteristics considered high risk: age younger than 50 years; black race; triple-negative tumors (absence of the three most common types of receptors known to fuel most breast cancer growth); and larger tumors (3 cm or less).

In addition, patients with two positive sentinel lymph nodes were twice as likely to undergo ALND as patients with one tumor-positive sentinel node. Patients whose tumor metastases measured 2 mm (the width of two grains of rice) or larger were more than three times likelier to undergo ALND compared with patients who had a smaller spread of the cancer, called micrometastases.