the SENOMAC trial

Omission of Axillary Clearance in Breast Cancer Patients With Sentinel Node Macrometastases: a Randomized Trial

Since the introduction of sentinel node biopsy in breast cancer, it has become clear that its use is reliable and reproducible. Today, it is clinical routine to not remove further lymph nodes from the axilla (arm pit) in case the sentinel node (which is the first lymph node/s reached by lymphatic flow from the breast) is free of tumor deposits. It is also routine to leave remaining lymph nodes behind in case the sentinel node contains a minimal cluster of tumor cells, called isolated tumor cells (formerly submicrometastasis). Even in slightly larger tumor deposits, so called micrometastasis (up to 2 mm in size), it has been shown that a completion axillary clearance (removal of further lymph nodes from the arm pit) does not contribute to a better survival. Data from a randomized study indicate that it seems safe to omit axillary clearance even if the sentinel node biopsy shows up to 2 nodes with tumor deposits over 2 mm in size (macrometastasis). These studies have changed clinical practice in many countries, however, it is still debated whether it is safe to omit axillary clearance in the case of sentinel node macrometastasis due to under-recruitment in the aforementioned study. The rationale for omitting extensive axillary surgery is the avoidance of postoperative morbidity such as arm lymphedema, loss of sensation, pain and swelling.

The hypothesis is that refraining from axillary clearance in breast cancer patients with 1-2 sentinel nodes with macrometastasis will not worsen overall survival by more than 2.5% after 5 years.

This study is a prospective multicenter randomized trial including the majority of centers in Sweden treating breast cancer. Planned accrual is 3000 patients.

Breast cancer patients without signs of axillary nodal involvement will be eligible for sentinel node biopsy. Those who are found to have up to two sentinel node containing macrometastasis will be informed about this trial Those wishing to participate will be randomized to either undergo further axillary surgery (clearance) or not. Outcome measures are overall and breast cancer-specific survival, disease-free survival and axillary recurrence, as well as patient-reported arm morbidity and quality of life.

The SENOMAC trial has randomized 2768 patients until December 31, 2021, and is now closed for further enrolment.