Patients with early-stage breast cancer who have ER-positive tumours and clinically node-negative axilla can forego sentinel lymph node biopsy without negative consequence.

Surgical management of early-stage breast cancer has evolved over the last two decades towards de-escalation. Surgeries have become less extensive and the question of whether any surgical intervention is need for the axilla remains open for debate.

In the prospective, noninferiority INSEMA trial, women with clinical stage T1 or T2 tumours, clinical axillary node–negative disease (both by examination and imaging with ultrasound) and a plan for breast-conserving surgery were randomised (one to four) to treatment without axillary surgery or to sentinel lymph node biopsy (SLNB). Patients undergoing SLNB found to have one to three macrometastases were further randomised to completion axillary dissection or no further axillary surgery (data not mature).

Among the per-protocol population of 4858 patients, 90% had clinical stage T1 tumours and 79% had surgically confirmed pathological T1 tumours. Approximately 98% of tumours were ER-positive and only 3.6% were HER2-positive. Postoperative adjuvant therapy was similar between groups, except slightly more patients in the surgery group received chemotherapy.

With a median follow up of 73.6 months, the omission of SLNB was noninferior to surgery for the primary endpoint of five-year invasive disease-free survival (91.9% and 91.7%). Incidence of axillary recurrence was 1.0% versus 0.3%, respectively, and incidence of death from any cause was 1.4% versus 2.4%. Not surprisingly, patients not undergoing SLNB had less arm oedema/pain and greater arm/shoulder mobility.

Comment: The INSEMA study, along with findings from other trials, confirms that SLNB can be avoided without compromise in local recurrence or survival in patients with clinical T1/T2, ER-positive tumours and clinically node-negative axilla. Since this profile fits an enormous subset of patients with early-stage breast cancer, applying these findings will result in de-escalation of treatment, decreases in therapy-related morbidity and no compromise in outcome.

William J. Gradishar, MD, Professor of Medicine and Director of Breast Medical Oncology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, USA.

Reimer T, et al. Axillary surgery in breast cancer – primary results of the INSEMA trial. N Engl J Med 2024 Dec 12; e-pub (https://doi.org/10.1056/ NEJMoa2412063).

This summary is taken from the following Journal Watch titles: Oncology and Hematology.