When is a completion axillary lymph node dissection necessary in the presence of a positive sentinel lymph node?

Background
The management of the axilla in the presence of positive sentinel lymph node (SLN) remains controversial. Many centres forgo completion axillary lymph node dissection (cALND) in the presence of micrometastatic disease. The American College of Surgeons Oncology Group (ACOSOG) Z0011 trialists argue for extending this to macrometastasis. The aim of this study was to correlate tumour burden in SLNs with that in the residual lymph node basin to determine the likelihood of residual disease in patients with micro- and macrometastasis in the SLN.

Methods
Patients who underwent cALND following a positive SLN were analysed for histopathological features of the primary tumour and burden of axillary disease.

Results
Of 155 patients, 115 (74%) had macrometastases and 40 (26%) micrometastases in the SLNs. Residual axillary disease was detected in 55/155 (35%) patients with macrometastases and 4/40 (10%) with micrometastases. Generally, with increasing size of metastasis in the SLN there was an increasing risk of further disease in residual lymph nodes. Logistic regression analysis showed increased odds ratios for further disease for all groups when compared with the <2 mm (micrometastasis) SLN group.

Conclusion
Patients may be advised to forgo cALND where the SLN contains isolated tumour cells or micrometastasis. Recommendations for proceeding to cALND can be based on the size of metastasis in the SLN, which relates to the risk of further disease in the residual axillary lymph nodes and subsequent regional recurrence.