Background: Patients with extremity and trunk wall STS with high malignancy grade and size larger than 5cm are considered at high risk of death, but in fact this risk varies broadly depending on histologic subtype and size. The Sarculator, a nomogram for STS, can improve prognostic assessment of these patients. This tool was evaluated for stratifying risk of distant metastasis (DM) and overall survival (OS) in a RCT investigating perioperative chemotherapy. Methods: High-risk STS patients were randomly assigned to receive either three cycles of preoperative chemotherapy with epirubicin (120 mg/m2) and ifosfamide (9 g/m2) or the same three preoperative cycles followed by two further postoperative cycles. The Sarculator was used to stratify patient risk according to predicted 10-year cumulative incidence of DM and OS rates. Results: The Sarculator identified three different prognostic groups of patients at low (N = 101), intermediate (N = 102), and high (N = 107) risk. Cumulative incidence of DM was 0.26 (SE: 0.04), 0.31 (SE: 0.05), and 0.48 (SE: 0.05) for low, intermediate, and high risk patients, respectively. Similarly, OS rates were 0.78 (95%CI 0.68-0.85), 0.63 (95%CI 0.53-0.72), and 0.42 (95%CI 0.32-0.52), respectively. Patients in the low risk group were at significantly lower risk of death compared to those in the intermediate (HR 0.51, 95%CI 0.34-0.78, P = 0.002) and high (HR 0.28, 95%CI 0.17-0.46, P < 0.001) risk groups. Subgroup analysis performed by jointly considering these three groups and the two study arms did not identify statistically significant survival differences between the treatment arms within each risk category. Conclusions: Patients with high-risk STS included in this RCT were not a homogeneous population. The Sarculator identified different risk groups for DM and OS even in patients included in a RCT investigating perioperative treatments. This tool should be considered for redefining high-risk STS and stratifying patient risk in future RCT investigating perioperative chemotherapy. Clinical trial information: 2004-003979-36.