Micrometastases in axillary lymph nodes and outcome of breast cancer
Hetterich M.1, Gerken M.2, Ortmann O.1, Klinkhammer-Schalke M.2, Ignatov A.1
1Universitätsfrauenklinik Regensburg, Caritas St. Josef Krankenhaus, Gynäkologie und Geburtshilfe, Regensburg, Deutschland, 2Tumorzentrum Regensburg, Institut für Qualitätssicherung und Versorgungsforschung der Universität Regensburg, Regensburg, Deutschland

Background: The axillary lymph node status is one of the most important prognostic factors in patients with primary breast cancer. Nodal micrometastases (pN1mi) are defined as nodal metastases with deposits from >0.2 ≤ 2mm. The impact of nodal micrometastases on overall survival (OS) and recurrence-free survival (RFS) of patients with breast cancer remains unclear. There are no recommendations concerning the performance of adjuvant chemotherapy. In this context, we aimed to investigate the impact of micrometastases on the clinical outcome of breast cancer patients depending on their adjuvant chemotherapy status.
Patients and methods: We performed a retrospective population-based register study with 26353 patients with primary breast cancer diagnosed between 2003 and 2017. After exclusion of 14070 patients 12283 were eligible for analysis: 11743 were node negative (pN0) and 540 with nodal micrometastases (pN1mi).
Results: Nodal micrometastases were associated with a reduced 10-year OS and RFS among women with early-stage breast cancer, who did not receive systemic adjuvant chemotherapy. This effect was abolished after adjustment for age, tumor size and grading. Furthermore, in the group of patients with nodal micrometastases the systemic chemotherapy treatment improved neither the OS (hazard ratio (HR) 1.51, 95% confidence interval (CI) 0.80-2.85) (p=0.208) nor the RFS (HR 1.12, 95%CI 0.63-1.97) (p=0.705) as demonstrated by multivariate cox-regression analysis.
Conclusions: Patients with nodal micrometastases show a comparable outcome to node negative patients.Chemotherapy did not improve significantly the outcome of breast cancer patients with nodal micrometastases. In this regard, nodal micrometastases should not be considered in the treatment decision.