Objectives: To 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).
Methods: Thirty 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.
Results: There 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.
Conclusion: Optimization 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.
Keywords: Chemotherapy; Magnetic resonance imaging; Response evaluation criteria in solid tumors; Sarcoma.