Incorporating sentinel chain involvement pattern to predict non-sentinel lymph nodes status in breast cancer after neoadjuvant chemotherapy.

[PURPOSE] Up to 60% of breast cancer (BC) patients with positive sentinel lymph nodes (SLNs) after neoadjuvant chemotherapy (NAC) had no metastatic non-sentinel lymph node (non-SLN). We aimed to establish a model incorporating sentinel chain involvement pattern to predict the non-SLN status.

[METHODS] SLNs were ranked in the order of fluorescent intensity, black staining degree, and lymphatic drainage to form a sentinel chain, which included three involvement patterns: sequential pattern (metastases are found in SLNs ranking ahead), skip pattern (metastases do not relate to the order of SLNs), and all involved pattern. The relationship between sentinel chain involvement pattern and non-SLN metastasis was explored.

[RESULTS] Of the 316 patients analyzed, 98.6% (71/72) of patients with all involved pattern, 58.9% (66/112) with skip pattern, and 13.6% (18/132) with sequential pattern had non-SLN metastases. The non-SLN metastasis rate in sequential pattern was significantly lower than that in the other two patterns (OR  = 15.83, 95% CI: 5.14-48.80, p < 0.001; OR  = 2.273, 95% CI: 0.15-35.56, p = 0.559). Multivariate logistic regression indicated that factors including sentinel chain involvement pattern, number of positive and negative SLNs, and primary tumor size were independent predictors of non-SLN. The model showed adequate discrimination, with AUC of 0.942 and 0.930 in training and validation cohort, respectively.

[CONCLUSION] The model demonstrated satisfactory performance in predicting non-SLN metastasis in BC patients with positive SLNs after NAC and had potential to select patients with low risk of non-SLNs metastasis who could avoid ALND.