BACKGROUND: Menacalc is an immunofluorescence-based, quantitative method in which expression of the non-invasive Mena protein isoform (Mena11a) is subtracted from total Mena protein expression. Previous work has found a significant positive association between Menacalc and risk of death from breast cancer. Our goal was to determine if Menacalc could be used as an independent prognostic marker for axillary node-negative (ANN) breast cancer.METHODS: Analysis of the association of Menacalc with overall survival (death from any cause) was performed for 403 ANN tumors using Kaplan Meier survival curves and the univariate Cox proportional hazards (PH) model with the log-rank or the likelihood ratio test. Cox PH models were used to estimate hazard ratios (HRs) for the association of Menacalc with risk of death after adjustment for HER2 status and clinicopathological tumor features.RESULTS: High Menacalc was associated with increased risk of death from any cause (P=0.0199, HR (CI)=2.18 (1.19, 4.00)). A similarly elevated risk of death was found in the subset of the Menacalc cohort which did not receive hormone or chemotherapy (n=142) (P=0.0052, HR (CI)=3.80 (1.58, 9.97)). There was a trend toward increased risk of death with relatively high Menacalc in the HER2, basal and luminal molecular subtypes.CONCLUSIONS: Menacalc may serve as an independent prognostic biomarker for the ANN breast cancer patient population.