Multicentre evaluation of intraoperative molecular analysis of sentinel lymph nodes in breast carcinoma

Background: Ideally, intraoperative sentinel lymph node (SLN) analysis in breast cancer should be automated, have high concordance with extensive histopathology, and be applicable in any hospital setting. A prospective multicentre evaluation of the one-step nucleic acid amplification (OSNA) automated molecular diagnostic system of SLN analysis was undertaken.

Methods: Intraoperative examination of SLNs from 204 patients with breast cancer was performed by OSNA at four sites in the UK. Half of each SLN was assessed by OSNA (for cytokeratin 19 mRNA) and the remaining half was paraffin embedded for intensive histological examination at ten levels. Discordant cases were reanalysed by further molecular biological techniques and by additional histological examination of all remaining nodal material to ascertain whether the discordance was due to an uneven distribution of metastases, known as tissue allocation bias (TAB).

Results: After exclusion of samples affected by TAB, the overall concordance rate for OSNA versus histopathology was 96.0 per cent, with a sensitivity of 91.7 per cent and a specificity of 96·9 per cent. The median time to process a single SLN was 32 (range 22-97) min, and that for two nodes 42 (30-73) min.

Conclusion: OSNA enables accurate automated intraoperative diagnosis and can be used successfully in different UK hospitals. When the SLN is shown to be positive, the patient can undergo immediate axillary clearance under the same anaesthetic rather than having a delayed second procedure.