The omission of axillary lymph node dissection did not lead to increases in adverse oncologic outcomes for patients with breast cancer and sentinel lymph node macrometastases, according to late-breaking research presented at the 2026 ASCO Annual Meeting.

In addition, the omission of axillary lymph node dissection appeared to reduce the incidence of arm-related morbidity, a frequent adverse event associated with the procedure.

In the randomized controlled SENOMAC study, researchers sought to determine whether patients with one or two sentinel lymph node macrometastases could safely omit axillary lymph node dissection. The study enrolled patients with primary invasive, clinically node-negative stage I-III breast cancer. Unlike previous trials, SENOMAC allowed patients with larger tumors and those undergoing mastectomy to enroll.

The study included data from 2540 patients treated in five countries, who were assigned to axillary lymph node dissection or omission. Overall survival (OS) served as the study’s primary endpoint, with breast cancer-specific survival acting as a secondary endpoint.

The researchers also employed the Lymph-ICF questionnaire to determine patient-reported arm morbidity, and EORTC QLQ-C30 and BR23 questionnaires were administered to determine patient-reported health-related quality of life.

The study had a median follow-up of 60.1 months. The return rates for questionnaires were 81.3% at 3 years and 74.6% at 5 years.

The researchers observed 176 deaths in the cohort, with 75 deaths attributed to breast cancer. The omission group had a 5-year OS of 94.4%, compared to 93.4% for the completion group.

The omission group had a 5-year breast cancer-specific survival rate of 97.8%, compared to 97.3% for the completion group.

According to Lymph-ICF data, patients in the omission group had significantly better physical arm functioning at 3 years and 5 years.

According to BR23 data, patients assigned to axillary lymph node dissection self-reported arm symptoms at a significantly higher rate than patients assigned to omission. This difference persisted significantly at 3 years and 5 years.

The researchers did not observe significant between-group differences in self-reported global health-related quality of life at the 3-year and 5-year intervals.

“Lymphedema can be a devastating quality-of-life issue that alters a woman's mobility, appearance, and self-esteem long after breast cancer treatment is complete. This rigorous, large-scale trial proves that we can safely skip invasive axillary node dissection in patients with limited nodal disease, and that by avoiding this additional surgery, we can drastically reduce long-term arm complications and improve arm function for breast cancer patients even years out from their diagnosis. These findings have the potential to simplify surgical management and meaningfully impact breast cancer survivorship for women throughout the world.”

- Jane Lowe Meisel, MD, FACSO, medical oncologist at Winship Cancer Institute of Emory University and an ASCO Expert in breast cancer

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Reference: https://www.asco.org/abstracts-presentations/258172

Disclosures: Some authors declared financial ties to drugmakers. This study was funded by the Swedish Cancer Society, the Swedish Scientific Council, the Nordic Cancer Union, and the Swedish Breast Cancer Association. See abstract for details.

By Cameron Kelsall

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