Axillary dissection might be omitted in selected breast cancer patients with positive sentinel node (SLN). Total tumor load (TTL) in SLN expressed by cytokeratin 19 (CK19) mRNA, detected by automated molecular technique-one-step nucleic acid amplification (OSNA), can quantitatively determine tumor burden in SLN. This study aimed to create nomogram to predict non-sentinel lymph node (NSLN) status.
Breast cancer patients were recruited at Division of Head Neck and Breast Surgery, Department of Surgery, Siriraj Hospital, Mahidol University, Thailand from November 2015 to January 2018. The patients with invasive breast cancer T1-T3, clinically negative axillary lymph node and able to give informed consent underwent SLN biopsy assessed by OSNA. The patients with positive SLN underwent axillary lymph node dissection. Correlations between TTL, clinicopathological parameters and NSLN status were analyzed by chi-square statistic and logistic regression. Model discrimination was evaluated using receiver-operating characteristic (ROC) analysis.
Total number of the patients who underwent SLN biopsy was 262. There were 85 patients with positive SLN. Mean age at diagnosis of the patients in this group was 54.52±11.66 years. NSLNs were positive in 37 patients. Larger tumor size (25.35±9.02 mm vs 37.78±16.88 mm) and presence of lymphovascular invasion (24.5% vs 67.6%) were the independent factor that predict positive NSLN. TTL expressed by CK19 mRNA copy number can discriminate NSLN status with the area under ROC curve of 0.784 (95%CI 0.683-0.885). At the cut off level at 6550 copies/μL, sensitivity, specificity, and negative predictive value were 86.49%, 57.14%, and 84.85%, respectively. Nomogram containing tumor size and SLN status can predict NSLN involvement with area under ROC curve of 0.827 (95%CI 0.737-0.918).
Nomogram using the results by OSNA technique can predict NSLN status and help in decision for axillary lymph node dissection.
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All authors have declared no conflicts of interest.