Micrometastasis in the sentinel lymph node of breast cancer does not mandate completion axillary dissection

To determine if micrometastatic disease in the sentinel lymph node is a predictor of non-sentinel lymph node (non-SLN) involvement in breast cancer.

Sentinel lymph node biopsy (SLN) is an accepted alternative to axillary dissection in staging breast cancer. If the SLN contains metastatic foci, the standard recommendation is completion axillary node dissection (CAD). However, a large subset of patients with metastasis limited to the SLN is unnecessarily subjected to the morbidity of CAD.

A retrospective review of prospectively gathered breast cancer patients having SLN was conducted. Patients with metastasis to the SLN were selected for analysis. Various clinicopathologic features were analyzed for association with metastasis to the non-SLN.

A total of 194 women underwent successful SLN dissection. Metastasis to the SLN was found in 48 patients (21 had micrometastases, 27 had macrometastases). Of those with micrometastases, 16 underwent CAD with 1 patient having metastasis to the non-SLN. In patients with macrometastases, 26 had CAD with 14 patients having non-SLN metastasis. Multivariable logistic regression identified only macrometastatic disease in the SLN as significantly associated with involvement of the non-SLN (P = 0.03). None of the patients with micrometastases, including those without CAD, has evidence of local recurrence to date (3-30 months).

This study demonstrates that the incidence of non-SLN involvement is low in SLN that contains only micrometastatic foci and is within the accepted range of the false-negative rate of SLN. This suggests that a CAD may be omitted in patients with micrometastatic disease.