The SENOMAC Trial: Skipping Completion Axillary Dissection in Certain Breast Cancer Cases Shows No Negative Impact

The study, published in the New England Journal of Medicine, found that omitting completion axillary lymph node dissection (ALND) in these patients did not negatively impact their recurrence-free survival.

Background

When breast cancer spreads, it often first travels to the lymph nodes under the arm (axillary lymph nodes). Sentinel lymph node biopsy (SLNB) is a procedure used to determine if cancer has spread to these nodes.

The Z0011 trial from the USA, along with the European AMAROS trial, previously demonstrated that the omission of axillary node dissection following a positive sentinel node biopsy does not result in an increase in recurrences, either in lymph nodes or throughout the body. However, these previous trials lacked extensive randomised patient data and did not include a significant number of patients who had undergone mastectomy. Furthermore, 40% of their patients had only micrometastases (less than 2mm) in the sentinel node biopsy. Thus, this recent trial aimed to address these limitations.

The SENOMAC Trial

The SENOMAC trial was a large, international, randomised phase 3 trial that enrolled 2766 patients with clinically node-negative primary T1 to T3 breast cancer with one or two sentinel-node macrometastases (more than 2mm in size). Patients were randomly assigned to either completion ALND or sentinel-node biopsy only. The study's primary endpoint was overall survival; however, the publication reports on the secondary endpoint of recurrence-free survival. Notably, this trial did not restrict its patient scope to those with non-palpable lymph nodes that were not suspicious on ultrasound. It broadened the inclusion criteria to also encompass patients who exhibited non-palpable axillary lymphadenopathy but demonstrated suspicious lymph nodes on ultrasound, which were subsequently confirmed as positive on Fine Needle Aspiration (FNA). This trial also included a substantial number of patients who had undergone mastectomy, accounting for over 30% of participants. Additionally, it reported that nearly 90% of patients in both groups received radiation to axillary lymph nodes.

Key Findings

  • Non-inferiority of omitting ALND: The 5-year recurrence-free survival was 89.7% in the sentinel-node biopsy-only group and 88.7% in the ALND group. This difference was not statistically significant, meaning omitting ALND was not inferior to the more extensive surgery.

  • High Proportion of Patients Receiving Nodal Radiation Therapy: Most patients (89.9% in the sentinel-node biopsy group and 88.4% in the ALND group) received radiation therapy that included the lymph nodes in the target area.

  • Consistent Results Across Subgroups: The study found no significant difference in outcomes between the two groups across different ages, tumour stages, tumour types, surgery types, and more.

Implications for Patients

These findings have significant implications for patients with breast cancer. The SENOMAC trial provides robust evidence to support omitting completion ALND in patients with clinically node-negative T1-T3 breast cancer and one or two sentinel-node macrometastases . It further asserts that completion axillary dissection does not contribute to reduced recurrences or enhanced survival rates. Instead, it merely increases the risk of lymphoedema.

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