Prediction and monitoring of the response to chemoradiotherapy in oral squamous cell carcinomas using a pharmacokinetic analysis based on the dynamic contrast-enhanced MR imaging findings

Objectives To evaluate whether a pharmacokinetic analysis is useful for both predicting and monitoring the response to chemoradiotherapy (CRT) in oral cancer. Methods Patients with oral squamous cell carcinoma treated with preoperative CRT and surgery were enrolled. They underwent dynamic contrast-enhanced MRI before (n=23), and after CRT (n=20). We estimated four parameters: arrival time of contrast medium (TA), exchange rate constant from the extracellular extravascular space (EES) to plasma (kep), elimination of contrast medium from the central compartment (kel) and an amplitude scaling constant (AH) using the Brix model. The histological evaluation of the effects of CRT was performed according to Ohboshi and Shimosato's classification. We analysed the correlation between the parameters and the histological evaluation. Results The pre-CRT AH between the responders and nonresponders was significantly different (P=0.046), however, the three parameters (TA, K _ep, K _el) were not significantly different among the groups (P=0.76, P=0.60, P=0.09). As AH decreased, the tumour response improved. The change in the AH between the pre- and post-CRT of responders was significantly higher than that of non-responders (P=0.043). Conclusion The AH, which is affected by the ratio of the EES, was an important parameter for predicting and monitoring the tumour response to CRT.