Purpose Intermediate-risk early breast cancer (EBC) is a heterogeneous group in which adjuvant chemotherapy decision proves to be difficult. Clinical and pathological criteria are sometimes insufficient to determine the best therapeutic options, and validated biomarkers such as uPA/PAI-1, are needed to contribute to the decision-making. The objective of this study was to evaluate the clinical outcome of an unselected ER+/HER2− pN0 EBC cohort of patients in whom the routine clinical decision process included a prospective uPA/PAI-1 determination. Method This monocentric retrospective study included 520 patients who underwent curative surgery in our institute between 2006 and 2011. Adjuvant therapeutic strategy was decided based on clinical–pathological data, altogether with a routine prospective determination of uPA/PAI-1 tumor levels using fresh, extemporaneously sampled tissue. We evaluated the correlation between uPA/PAI-1 levels, clinical-pathological variables, and the patient’s outcome (relapse-free survival, RFS, and overall survival, OS). Result Median follow-up was 5.4 years. The 5- and 10-year RFS rates were ,respectively, 95 and 89%, and the five-year OS rate was 96.3%. Forty percent of tumors had low uPA/PAI-1 levels. Seventy-five percent of patients with low uPA/PAI-1 levels did not receive chemotherapy, when 25% did. Sixty percent of patients with high uPA and/or PAI-1 levels received chemotherapy, while 40% did not. No statistical significant correlation was found between the uPA/PAI-1 levels and RFS or OS. Conclusion The personalization of the patients’ treatment using uPA/PAI-1 tumor levels allows the reversion of the well-known poor prognostic impact of high uPA/PAI-1 levels and strongly supports the use of this biomarker in clinical practice.