LAUSR

AIMS To determine if there is any correlation between the number of positive non-sentinel lymph nodes (NSLN) and the mRNA copy numbers of cytokeratin 19 receptor on one step nucleic acid amplification (OSNA) in the sentinel lymph node (SLN). METHODS An 8-year retrospective study of consecutive patients who had primary surgery and sentinel node biopsy for breast cancer from January 2011 to December 2018 was carried out. All these patients had intra-operative analysis of sentinel lymph nodes by OSNA. Patients who had neoadjuvant chemotherapy or neoadjuvant endocrine therapy were excluded. RESULTS There were 1159 patients with an age range of 24 to 90 years and a mean age of 63 years in this study. A total of 1324 SLNs were analyzed by OSNA. Macrometastasis was found in 120 patients and they underwent axillary lymph node dissection (ALND). A total of 2405 NSLNs were analyzed. Of the patients who had ALND, 51 (43%) patients had negative NSLNs and 69 (57%) had positive NSLNs. The mean mRNA copy numbers respectively for the 2 groups were 853,665 and 609,855. The difference between the means is not statistically significant (P = 0.82). Also the Receiver Operating Characteristic (ROC) Curve of the total CK-19 mRNA copy number for both groups-negative and positive NSLN were almost identical (Figure 3) indicating mRNA copy numbers cannot be used to discriminate between positive and negative non-sentinel lymph nodes. CONCLUSION It is clear from our study that in patients who have ALND due to macromets on OSNA, there is no correlation between the total tumor load as represented by mRNA copy numbers and the likelihood of positive non-sentinel lymph nodes. We therefore cannot rely solely on the mRNA copy numbers to decide on ALND.