Predictive Effect of the Er/Ki67 Ratio on Axillary Metastasis in Breast Cancer Patients.

BACKGROUND: To evaluate whether the estrogen receptor (ER)/Ki67 ratio is associated with additional nonsentinel lymph node metastasis in breast cancer patients with negative preoperative axillary assessment but a positive sentinel lymph node biopsy (SLNB). PATIENTS AND METHODS: This retrospective study included 87 women with invasive breast cancer, no clinical or imaging evidence of axillary metastasis, a metastatic sentinel lymph node, and completion axillary lymph node dissection (ALND). Clinicopathological and nodal variables, including ER expression, Ki67, and the ER/Ki67 ratio, were analyzed. Receiver operating characteristic analysis was used to identify the optimal ER/Ki67 cutoff for additional nonsentinel lymph node metastasis. RESULTS: The detailed nodal distribution showed that 50 of 87 patients had no additional metastatic lymph nodes beyond the sentinel node, whereas 37 had further axillary involvement. An ER/Ki67 ratio of 3.0833 yielded an area under the curve of 0.893, with sensitivity of 0.811 and specificity of 0.878; ratios above this cutoff were associated with a lower likelihood of additional metastasis. CONCLUSION: A higher ER/Ki67 ratio was associated with a lower probability of additional nonsentinel lymph node metastasis in this selected cohort. The ratio may support multidisciplinary risk stratification but should not be used alone to perform or omit completion ALND. External validation in larger contemporary cohorts is required.