ObjectivesTo determine the acquisition delay after gadolinium-chelate injection that optimizes the prediction of the histological response during anthracycline-based neoadjuvant chemotherapy (NAC) for locally advanced high-grade soft-tissue sarcomas (STS).MethodsThirty patients (mean age 62 years) were included in this IRB-approved study. All patients received 5-6 cycles of NAC followed by surgery. A good response was defined as ≤ 10% viable cells on histological analysis of the surgical specimen. DCE-MRI was performed before treatment (MRI0) and after two cycles (MRI1). Images were obtained every 8 s. Change in contrast enhancement (CE) between MRI0 and MRI1 was calculated for each acquisition delay ‘t’ on the whole tumor volume. Area under the receiver-operating characteristics curves (AUROC) for change in CE was calculated at each acquisition delay, as well as the accuracy of the Choi criteria.ResultsThere were 22 (73.3%) poor responders. Acquisition delay had a significant effect on change in CE and on the response status according to Choi (p = 0.0014 and 0.0270, respectively). The highest AUROC was obtained at t = 58 s (0.792) with an optimal threshold of a -30.5% decrease in CE. At t = 58 s, accuracy to predict a poor response was 82.8% above this threshold, while it was 72.4% and 70% with no objective response according to the Choi criteria and RECIST1.1, respectively.ConclusionOptimization of acquisition delay after injection to estimate change in CE improves the prediction of histological response. For STS undergoing NAC, a 60-s delay can be recommended with MRI.Key points• Accuracy of response criteria based on contrast enhancement, like the Choi criteria, is dependent on the acquisition delay after gadolinium-chelate injection.• DCE-MRI helps determine the optimal acquisition delay after gadolinium-chelate injection for improving evaluation of tumor response.• In soft tissue sarcoma, an acquisition delay at 60 s optimizes the evaluation of the response and accuracy of the Choi criteria.