Abstract Aim Final 10-year analysis of the prospective randomised Chemo-N0 trial is presented. Based on the Chemo-N0 interim results and an European Organisation for Research and Treatment of Cancer (EORTC) pooled analysis ( n = 8377), American Society of Clinical Oncology (ASCO) and Arbeitsgemeinschaft Gynäkologische Onkologie (AGO) guidelines recommend invasion and metastasis markers urokinase-type plasminogen activator (uPA)/plasminogen activator inhibitor-1 (PAI-1) for risk assessment and treatment decision in node-negative (N0) breast cancer (BC). Methods The final Chemo-N0 trial analysis (recruitment 1993–1998; n = 647; 12 centres) comprises 113 (5-167) months of median follow-up. Patients with low-uPA and PAI-1 tumour tissue levels ( n = 283) were observed. External quality assurance guaranteed uPA/PAI-1 enzyme-linked immunosorbent assay (ELISA) standardisation. Of 364 high uPA and/or PAI-1 patients, 242 agreed to randomisation for CMF chemotherapy ( n = 117) versus observation ( n = 125). Results Actuarial 10-year recurrence rate (without any adjuvant systemic therapy) for high-uPA/PAI-1 observation group patients (randomised and non-randomised) was 23.0%, in contrast to only 12.9% for low-uPA/PAI-1 patients ( plog-rank = 0.011). High-risk patients randomised to cyclophosphamide-methotrexate-5-fluorouracil (CMF) therapy had a 26.0% lower estimated probability of disease recurrence than those randomised for observation (intention-to-treat (ITT)-analysis: hazard ratio (HR) 0.74 (0.44–1.27); plog-rank = 0.28). Per-protocol analysis demonstrated significant treatment benefit: HR 0.48 (0.26–0.88), p = 0.019, disease-free survival (DFS) Cox regression, adjusted for tumour stage and grade. Conclusions Chemo-N0 is the first prospective biomarker-based therapy trial in early BC defining patients reaching good long-term DFS without adjuvant systemic therapy. Using a standardised uPA/PAI-1 ELISA, almost half of N0-patients could be spared chemotherapy, while high-risk patients benefit from adjuvant chemotherapy. These 10-year results validate the long-term prognostic impact of uPA/PAI-1 and the benefit from adjuvant chemotherapy in the high-uPA/PAI-1 group at highest level of evidence. They thus support the guideline-based routine use of uPA/PAI-1 for risk-adapted individualised therapy decisions in N0 breast cancer.