Is OSNA better than imprint cytology for intraoperative diagnosis of cancer involvement of axillary sentinel node in breast cancer?

OBJECTIVE: The study aim was to establish Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value (NPV), and Accuracy Values of both imprint cytology (IC) and the OSNA assay for intraoperative assessment of axillary sentinel node (SN) cancer involvement in breast cancer. Specifically, we wished to find out if true positive and false negative results of IC were associated to axillary lymphadenectomy (ALND). Also, we addressed a comparative cost analysis between techniques.

METHODS: 244 patients treated for breast cancer in the Breast Unit of Hospital Germans Trias i Pujol from 2011 to 2015 were prospectively included. A transversal, consecutive design was applied to assess IC compared to the reference test (OSNA). Inclusion criteria were: T1 and T2 tumors with negative nodes, both clinically and on ultrasound.

RESULTS: Sensitivity of IC for macrometastases was 70%. The NPV of IC for macrometastases was 95,75%. Accuracy of IC was 96,12%. In the comparative cost analysis, the release time of results for OSNA doubled that of IC and was associated with an increased cost of € 370.

CONCLUSIONS: IC has been stated as a good technique for intraoperative cancer involvement SN with high sensitivity and NPV compared to the OSNA assay. It allows keeping the whole node tissue and thus the possibility of improved histopathological evaluation, which can be useful for adjuvant, and offers the advantage of being less time consuming. Cost analysis shows a higher cost for OSNA, which may exceed the benefit of sorting out false negatives from IC.