Survival and axillary recurrence following sentinel node-positive breast cancer without completion axillary lymph node dissection – the randomized SENOMAC trial

The role of completion axillary lymph node dissection (ALND) in sentinel node (SN)-positive breast cancer is questioned since key randomized trials showed no survival differences comparing completion ALND and SN biopsy alone.

These trials however were significantly underpowered, and in addition, patients undergoing mastectomy or those with larger tumors were not included.

Thus, there is a need for additional prospective data validating previous results with sufficient statistical power to detect even smaller survival differences, and including the crucial subgroup of mastectomy patients.

The SENOMAC trial was initiated in 2015 as an international randomized phase 3 clinical trial including patients with clinically node-negative T1-T3 breast cancer and up to two SN macrometastases.

Patients are randomized 1:1 to undergo completion ALND or not, and both breast-conserving surgery and mastectomy are eligible interventions.

The non-inferiority endpoint is overall survival at 5-years with a non-inferiority margin of 2.5% (94% versus 91.5%), targeting an overall accrual of 3000 patients.

Secondary endpoints such as arm morbidity and health-related quality of life are measured by patient-reported outcomes (PROs) at 1, 3 and 5-years. The SENOMAC Trial has to date including 2395 patients, 34% of whom operated by mastectomy, from 5 European countries. Enrolment will be closed at the end of 2021, and the first report on the primary endpoint is expected in 2024.