Prognostic Significance of Lymph Node Examination by the OSNA Method in Lung Cancer Patients—Comparison with the Standard Histopathological Procedure

The aim of the study was to compare the prognostic significance of lymph node status of patients with lung cancer analyzed by three different methods: hematoxylin and eosin (H&E), immunohistochemistry of cytokeratin 19 (IHC CK19), and One-Step Nucleic Acid Amplification (OSNA). The clinical relevance of the results was evaluated based on relation to prognosis; the disease-free interval (DFI) and overall survival (OS) were analyzed. During radical surgical treatment, a total of 1426 lymph nodes were obtained from 100 patients, creating 472 groups of nodes (4–5 groups per patient) and examined by H&E, IHC CK19 and OSNA. The median follow-up was 44 months. Concordant results on the lymph node status of the H&E, IHC CK19 and OSNA examinations were reported in 78% of patients. We recorded shorter OS in patients with positive results provided by both OSNA and H&E. The study demonstrated a higher percentage of detected micrometastases in lymph nodes by the OSNA method. However, the higher sensitivity of the OSNA, with the cut-off value 250 copies of mRNA of CK19/µL, resulted in a lower association of OSNA positivity with progress of the disease compared to H&E. Increasing the cut-off to 615 copies resulted in an increase in concordance between the OSNA and H&E, which means that the higher cut-off is more relevant in the case of lung tumors.

May axillary dissection be avoided after micro metastases in sentinel lymph node analyzed by OSNA method?

18 Background: The study of the sentinel node biopsy is a common method to assess axillary involvement before surgical resection. The OSNA assay based on reverse transcriptase loop mediated amplification (RT-LAMP) and quantification of cytokeratin 19 (CK19) mRNA allows a rapid intra-operative detection of the metastases in the sentinel lymph node in breast cancer patients. Pathologists considered micro metastases when the size of the node involvement was between 0.2 and 2 mm and the OSNA method assess micro metastases when the copy number of CK19 is between 250 and 5000. Methods: From a total of 341 patients in which sentinel node had been analyzed, we studied a series of 32 patients whose sentinel nodes had micro metastases assessed by OSNA and who underwent subsequent axillary dissection. Median breast tumour size was 1.6 cm, 10 patients (31%) had less than 1 cm in size and only 6 patients (19%) had >2 cm. 78% of patients shown positive oestrogen receptor and 14 patients (44%) had low Ki67 (<14%). The CK19 mRNA was quantified in all patients (32) resulting in a median value of 540 (210-4800). Results: The median value of the nodes removed by axillary dissection was 14 (9-19). We found tumor invasion in none of them by histopathological conventional study. Conclusions: Since we have found no axillary involvement when the sentinel node have micro metastases analyzed by the OSNA method it seems that quantitative measure of CK19 by OSNA may be a useful procedure in order to avoid axillary dissection, although it would be necessary to perform larger studies to demonstrate this effect.