Background: The advent of sentinel lymph node biopsy (SLNB) and improvements in histopathological and molecular analysis have increased the detection rate of nodal micrometastases. As compare with conventional method, the one-step nucleic acid amplification (OSNA) assay might detect higher cases of SLN micrometastases.

Objective: The present study aimed to assess the impact of OSNA assay on micrometastases detection rate and potential benefit in terms of adjuvant treatment and survival outcome in early breast cancer.

Materials and Methods: A retrospective review of patients with sentinel node (SLN) micrometastasis detected by the OSNA assay between 2015 and 2019 was carried out. Clinicopathological, adjuvant treatment, and follow-up data were collected. Ten-year survival benefit with adjuvant chemotherapy was calculated using PREDICT online, version 1.2 (https://breast.predict.nhs.uk/).

Results: Between November 2015 and December 2019, 78 out of 721 patients (10.8%) were positive for micrometastasis based on OSNA detection. Three-fourth of cases received adjuvant systemic chemotherapy and 57% were given taxane-based regimen. Using the PREDICT online tool, an estimated 10-year survival in patients who received adjuvant systemic chemotherapy and who did not, were 75% and 66%, respectively (p=0.018). A 10-year survival benefit from chemotherapy among patients who received systemic chemotherapy was 8% compared with 4% with no-adjuvant-therapy cohort.

Conclusion: The OSNA assay allows for a more precise detection of SLN micrometastasis compared to conventional pathology and could guide therapeutic decision making. In patients with micrometastasis who received adjuvant systemic chemotherapy, the estimated overall 10-year survival was improved.

Keywords: Axillary staging, Breast cancer, Micrometastases, OSNA, Sentinel lymph node biopsy

DOI: doi.org/10.35755/jmedassocthai.2021.05.12056

Received 17 September 2020 | Revised 12 February 2021 | Accepted 19 February 2021