Support for Omitting SLNB in Some Early Breast Cancers

SAN ANTONIO — Recent findings from the INSEMA trial provided more evidence that omitting axillary sentinel lymph node biopsy (SLNB) does not compromise survival in women with low-risk, early-stage invasive breast cancer undergoing breast-conserving surgery.

Among patients with clinically node-negative, stage T1 or T2 invasive breast cancer, the 5-year invasive disease-free survival (DFS) rate was about 92% with or without SLNB, and the estimated 5-year overall survival rate was similar between the groups — 98.2% without SLNB and 96.9% with SLNB.

This de-escalation strategy appeared to be safe in this patient population, according to study investigator Toralf Reimer, PhD, with University of Rostock, Rostock, Germany, who presented findings from the INSEMA trial at San Antonio Breast Cancer Symposium (SABCS) 2024. The trial results were also simultaneously published in The New England Journal of Medicine.

Hot Area of Study 

INSEMA trial is one of the four ongoing de-escalation trials evaluating omitting axillary surgery in patients who receive upfront breast-conserving surgery, Reimer told attendees.

Results of the SOUND trial published last year demonstrated that undergoing or omitting axillary surgery in patients with small breast cancer (no larger than 2 cm) led to essentially the same 5-year DFS and overall survival rates in both groups.

The goal of the INSEMA trial was to demonstrate that complete omission of axillary surgery does not compromise invasive DFS outcomes in patients with early breast cancer who received breast-conserving surgery.

The INSEMA trial enrolled 5502 patients with clinically node-negative invasive breast cancer staged as T1 or T2 (tumor size ≤ 5 cm) who underwent breast-conserving surgery and postoperative full breast irradiation. Overall, 90% of patients had clinical T1 cancer, the median age at cancer diagnosis was 62 years, and almost all patients had hormone receptor–positive, human epidermal growth factor receptor 2–negative disease.

In the per-protocol population of 4858 patients, 3896 underwent SLNB and 962 did not.

After a median follow-up of 73.6 months, the estimated 5-year invasive DFS rate in the per-protocol population (primary outcome) was 91.9% in patients who omitted SLNB and 91.7% in those who had SLNB (hazard ratio, 0.91; 95% CI, 0.73-1.14). There were no between-group differences in distant relapse — 2.7% in both groups.

As expected, said Reimer, the rate for axillary recurrence was slightly higher in the no SLNB group than in the SLNB group (1.0% vs 0.3%), “but the absolute number of events is very low.”

The 5-year estimated overall survival rates were similar in the two groups as well — 98.2% without SLNB and 96.9% with SLNB.

As expected, compared with SLNB, omitting SLNB significantly reduced lymphedema (5.7% vs 1.8%), arm mobility restrictions (3.5% vs 2.0%), and pain with arm or shoulder movement (4.2% vs 2.0%).

Practice-Changing Findings?

Discussant for the study Puneet Singh, MD, breast surgeon at MD Anderson Cancer Center, Houston, said INSEMA “adds to the evidence that sentinel lymph node biopsy can be omitted in select patients” and not compromise survival outcomes or rates of recurrence.

Omitting SLNB “is appropriate for tumors 2 cm or smaller, as we know that higher rates of sentinel node positivity exist with larger tumors, and that has implications on adjuvant therapies,” Singh said.

She cautioned, however, that SLNB “is still a staging modality that is necessary for many patients, and therefore shared decision-making with patients and the multidisciplinary team is critical when determining who we can omit the sentinel biopsy without compromising their care. It’s really important to engage patients when we’re making these decisions.”

Richard J. Bleicher, MD, chief, Division of Breast Surgery, Fox Chase Cancer Center, Philadelphia, told Medscape Medical News, that while the INSEMA trial is “not immediately practice-changing, it definitely contributes to a trend that will get us there.”

The concept of eliminating SLNB “makes sense, in that we have longstanding data as far back as the Danish Breast Cancer Cooperative Group in the 1980s showing that no matter how many nodes you remove, there is no survival benefit,” noted Bleicher, who wasn’t involved in the study.

Trials published to date “lay a good foundation for sentinel node omission, and I suspect that BOOG 2013-08 and NAUTILUS will ultimately solidify this as standard where the burden of axillary disease is limited,” Bleicher said.

Funding for the INSEMA trial was provided by the German Cancer Aid, Bonn, Germany.

Disclosures for study authors are available at NEJM.org. Singh and Bleicher had no relevant disclosures.