Rate of metastasis in examined lymph nodes as a predictor of extracapsular extension in patients with axillary node-positive breast cancer.

BACKGROUND The status of the axillary lymph nodes is an important factor in the prognosis and treatment of breast cancer. Extracapsular extension (ECE) is the spread of lymphatic tumor cells beyond the capsule of an axillary lymph node. Recent studies have demonstrated that ECE is a strongly unfavorable prognostic factor. OBJECTIVE In the present study, we investigated whether the rate of metastasis among examined lymph nodes can be used to predict ECE in patients with axillary node-positive breast cancer. METHODS The subjects were 95 women with axillary node-positive breast cancer. The numbers of lymph nodes removed (examined) and lymph nodes involved were recorded. The cut-off values, area under the curve, sensitivity, and specificity were calculated with the receiver operating characteristic curve technique for ability of the rate of metastasis to examined lymph nodes to predict ECE. RESULTS The rate of metastasis to examined lymph nodes was significantly greater in patients with ECE than in patients without ECE [0.57 (0.03-1.00) vs. 0.22 (0.04-1.00), respectively, p: 0.001]. Similarly, the presence of vascular infiltration was significantly higher in patients with ECE than in those without ECE [30 (73.2%) vs. 25 (47.2%) respectively, p: 0.010]. On the other hand, other variables did not differ between the groups (p>0.05). When the cut-off value was ≥0.23, the sensitivity and specificity of the rate of metastasis to examined lymph nodes were 80.49% and 55.56%, respectively. The area under the curve was 0.697 (95% confidence interval: 0.594-0.787, p: 0.004). CONCLUSION Our results suggest that rate of metastasis among examined lymph nodes is a predictor of ECE in patients with axillary node-positive breast cancer.