Predictors of non-sentinel lymph node (non-SLN) metastasis in patients with sentinel lymph node (SLN) metastasis in endometrial cancer.

Objectives: The aim of this study was to determine the risk of metastasis in the remaining non-SLNs when the SLN is positive and to identify the factors that can predict this risk.

Methods: We reviewed all patients who underwent primary surgery for endometrial carcinoma with lymphadenectomy and SLN mapping (November 2010-November 2013) in our center. SLNs were ultra-staged on final pathology.

Results: A total of 268 patients were included. Overall, 43/268 patients (16%) were found to have SLN metastasis: macro-metastasis in 24 patients, micro-metastasis in 7 and ITC in 12. Non-SLN metastases were found in 15 of the 43 patients (34.8%) with positive SLN. Size of the SLN metastasis was the only factor associated with an increased likelihood of non-SLN metastasis (p=0.005). When the size of the SLN metastasis was ≤2mm, the risk of having another positive lymph node was only 5%, conversely, when the size of the SLN metastasis was >2mm, the risk of having another positive lymph node was 60.8% (p<0.0001). Histologic type, grade, depth of myometrial invasion, LVSI, cervical stromal invasion and CA-125 were not predictive.

Conclusion: When the SLN is positive, the risk of metastasis in the remaining non-SLNs was 34.8%. Size of the metastasis within the SLN was the only factor that could predict the risk of non-SLN metastasis; 2mm seems to be the cutoff size below which the risk of non-SLN metastasis is low.