Axillary lymph node micrometastases decrease triple-negative early breast cancer survival.

Background: Triple-negative breast cancers (TNBCs) are the most deadly form of breast cancer (BC) subtypes. Axillary lymph node involvement (ALNI) has been described to be prognostic in BC taken as a whole, but its prognostic value in each subtype is unclear. We explored the prognostic impact of ALNI and especially of small size axillary metastases in early TNBCs.
Methods: We analysed in this multicentre study all patients treated for early TNBC in 12 French cancer centres. We explored the correlation between clinicopathological data and ALNI, with a specific focus on the dichotomisation between macrometastases and occult metastases, which is defined as the presence of isolated tumour cells or micrometastases. The prognostic value of ALNI both in terms of disease-free survival (DFS) and overall survival (OS) was also explored.
Results: We included 1237 TNBC patients. Five-year DFS and OS were 83.7% and 88.5%, respectively. The identified independent prognostic features for DFS were tumour size >20 mm (hazard ratio (HR)=1.86; 95% CI: 1.11-3.10, P=0.018), lymphovascular invasion (HR=1.69; 95% CI: 1.21-2.34, P=0.002) and ALNI both in case of macrometastases (HR=1.97; 95% CI: 1.38-2.81, P<0.0001) and occult metastases (HR=1.72; 95% CI: 1.1-2.71, P=0.019). DFS and OS were similar between tumours with occult metastases and macrometastases. Tumours presenting at least two pejorative features (out of ALNI, lymphovascular invasion and large tumour size) displayed a significantly poorer DFS in both the training set and validation set, independently of chemotherapy administration. Tumours with no more than one of the above-cited pejorative features had a 5-year OS of ⩾90% vs 70% for other cases (P<0.0001).
Conclusions: Axillary lymph node involvement is a key prognostic feature for early TNBC when isolated tumour cells were identified in lymph nodes. This impact is independent of chemotherapy use.