Results from the phase 3 SENOMAC clinical trial found that omitting an axillary lymph node dissection (ALND) was safe for people with breast cancer that has spread to 1 or 1 sentinel lymph nodes, as it helped them avoid arm-related side effects known to impact quality of life.

The research was presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, which took place May 29 to June 2 in Chicago.

“After previous trials, it was unclear whether the omission of ALND could also be offered to patients receiving a mastectomy or those with larger tumours. The key finding is that more axillary surgery in itself does not improve survival in these patients.

This is extremely important because it means that axillary surgery should be seen as a diagnostic instrument, not a therapeutic tool,” said lead study author Jana de Boniface, MD, PhD, Department of Surgery, Capio St. Göran's Hospital and Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

The trial included 2,540 people with T1 to T3 breast cancer and up to 2 sentinel lymph node macrometastases.

T1 to T3 tumours have not grown into the chest wall or skin, and they range in size from 0.1 centimeter to more than 5 centimeters.

The median age of study participants was 61. Most participants had estrogen receptor-positive cancer (93.6%), and slightly over 1 in 3 had a mastectomy (36.3%).

After receiving a SLNB that showed up to 2 macrometastases, the participants were randomly assigned either to receive an ALND (1,205 people) or not to receive an ALND, called the omission group (1,335 people).

Both groups received adjuvant treatment according to the current standards of care, which often includes radiation therapy to the regional lymph nodes.

To assess arm-related side effects, the participants responded to questionnaires 1 year, 3 years, and 5 years after they were randomly assigned to a treatment group. These included: 

The Lymph-ICF questionnaire, which asks questions related to the impact of arm lymphoedema, such as how well a person can lift heavy objects or drive a car. The participants rated their problems on a scale of 0 to 10, resulting in a total score of 0 to 100. A score of 0 means no arm problems, and a score of 100 means the most severe arm problems.

The EORTC QLQ-BR23 questionnaire, which asks questions related to breast cancer-specific side effects, including arm symptoms. Scores from this questionnaire range from 0 to 100, with a higher score meaning more symptoms.

Key findings

After a median follow-up of 60.1 months:

• The 5-year overall survival rate was similar between groups, with 93.4% of participants still alive at 5 years in the ALND group compared to 94.4% of participants in the omission group.
• The 5-year breast cancer-specific survival was 97.2% in the ALND group vs. 97.9% in the omission group. 
• Overall, 203 participants died, 74 of them from breast cancer.
• In addition, the participants who did not have an ALND reported significantly better arm function at 1, 3, and 5 years after treatment than those who had an ALND:
  • Based on the Lymph-ICF questionnaire scores, those who did not receive an ALND had an average score difference of 10.64 at 1 year, 10.73 at 3 years, and 10.75 at 5 years, indicating better self-reported arm function.
  • Based on the EORTC questionnaire scores, fewer arm problems were reported in the omission group. At 1 year, there was an average score difference of 10.90. At 3 years, the average score difference was 9.86, and at 5 years, it was 10.02.
  • Response rates to the questionnaires were 83% at 1 and 3 years and 81% at 5 years.

“Lymphoedema 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,” said Jane Lowe Meisel, MD, FACSO, medical oncologist at Winship Cancer Institute of Emory University and an ASCO Expert in breast cancer.

The researchers are starting another randomised trial, called SENOMAC-ULTRA, to compare ALND against targeted axillary dissection, which removes significantly fewer lymph nodes, in people with known spread of the cancer to the lymph nodes in the armpit. They are also conducting the randomised T-REX trial to evaluate the omission of nodal radiation therapy in patients with estrogen receptor-positive breast cancer and 1 to 2 sentinel lymph node metastases who do not receive an ALND.

Source: American Society of Clinical Oncology