Radiotherapy for the treatment of "minimal" positive axillary lymph nodes in patients with early-stage breast cancer was comparable in efficacy and was associated with a significantly lower rate of the feared side effect of lymphedema compared to surgery, new 10-year data from a major randomized trial indicate.

The findings come from the European AMAROS (After Mapping of the Axilla Radiotherapy Or Surgery) study. The trialists followed 1425 patients with clinically node-negative breast cancer and minimal nodal involvement (one to three nodes) whose results of sentinel lymph node biopsy were positive. The patients were randomly assigned to receive either axillary surgery or radiotherapy.

The radiotherapy group

At 10 years, 1.82% (11 of 681 patients) of the radiotherapy group had experienced an axillary recurrence, compared with 0.93% (seven of 744 patients) of the axillary lymph node dissection group (hazard ratio, 1.71; P = .37).

For both groups of patients, this is an "extremely low" rate of lymph node recurrence, which was the primary endpoint, said principal investigator Emiel Rutgers, MD, Ph.D., a surgical oncologist at the Netherlands Cancer Institute in Amsterdam.

Rutgers was presenting the results here at the San Antonio Breast Cancer Symposium (SABCS) 2018. Study discussant Wendy Woodward, MD, a radiation oncologist at the MD Anderson Cancer Center in Houston, Texas, agreed about the axillary recurrence rates. "The rate of axillary failure was very low," she said.

There were also no significant differences between treatment arms for disease-free survival and overall survival. Both treatment approaches provide "excellent and comparable" locoregional control, summarized Rutgers.

"The trial, which had a noninferiority design, is an endorsement of radiotherapy, which "can be considered standard procedure," said Rutgers. That endorsement is boosted by the lower rates of lymphedema in the group that received radiotherapy.

At 5 years, 29.4% of the surgery group had lymphedema (determined by observation or treatment), vs 14.6% of the radiotherapy group (P < .0001). Notably, also at 5 years, 18.2% of the surgery group had undergone treatment for lymphedema, vs only 6.6% of the radiotherapy group (P < .0001).

This is "the beauty of de-escalation" — reducing morbidity without compromising outcomes, said Virginia Kaklamani, MD, of UT Health San Antonio, who moderated the press briefing.