METHODS: Patients who underwent SLNB for invasive breast cancer and were found to have positive SLN in two or fewer nodes were evaluated. The associations between non-SLN metastasis and clinicopahological factors were examined. Statistical analyses were performed using the Mann-Whitney and Chi-square tests, with statistical significance set at P < 0.05.
RESULTS: A total of 358 patients were enrolled during the study period and all of these patients were female and 54 patients had SLN metastasis (15%). Positive SLN in two or fewer nodes was identified in 44 patients (81.5%). Among these patients, 17 (38.6%) were found to have non-SLN metastasis. Non-SLN metastasis was associated with invasive tumor size (P = 0.015) and lymphatic involvement (P = 0.035). Multivariate analysis showed that tumor size (P = 0.011) and lymphatic involvement (P = 0.019) remained significant independent predictors of non-SLN metastasis, and that an invasive tumor size cut-off point of 28 mm was useful for dividing patients with positive SLN in two or fewer nodes into non-SLN-positive and non-SLN-negative groups.
CONCLUSIONS: Non-SLN metastasis was found in more than 30% of patients with SLN metastasis present in two or fewer nodes. Large tumor size and the presence of lymphatic involvement were significantly associated with non-SLN metastasis.