Lei Tang MD, Presenter: Nothing to Disclose

Ying-Shi Sun MD, PhD, Abstract Co-Author: Nothing to Disclose

Zi-Yu Li, Abstract Co-Author: Nothing to Disclose

Xiao-Peng Zhang MD, Abstract Co-Author: Nothing to Disclose

Jia-Fu Ji, Abstract Co-Author: Nothing to Disclose

Xiaoting Li, Abstract Co-Author: Nothing to Disclose

Lin Shen, Abstract Co-Author: Nothing to Disclose

To investigate the performance of quantitative parameters provided by MRI in the early prediction of the response of gastrointestinal stromal tumor (GIST) to targeted therapy.

The institutional review board approved this prospective MRI study. All of the patients signed the written informed consent. MRI examinations were performed in 62 patients with GIST on 1.5T scanner before and at 2 and 12 weeks after treatment with targeted agents (Imatinib mesylate, 44 cases; Sunitinib malate, 18 cases). The longest diameter (LD) and contrast-to-noise ratio (CNR) of the tumors were measured on T2-weighted images (T2WI), and the apparent diffusion coefficient (ADC) was measured on diffusion-weighted images (DWI). A maximum of two lesions per organ/site and five lesions per patient were enrolled according to the regulation of RECIST 1.1. The early percentage changes (%Δ) of the above three parameters were compared for their performance in the differentiation of the good response (GoodR) and poor response (PoorR) groups using ROC curves.

Total of 141 GIST lesions in 62 patients enrolled in the study. There were 42 patients in GoodR group and 20 in PoorR group. After two weeks of therapy, the percentage changes of the ADC and LD were significantly different between the two groups (ADC: GoodR 30% vs. PoorR 1%, Z = -4.819, P Z = -3.238, P =0.001), but not of the T2WI-CNR (GoodR -3% vs. PoorR -9%, Z = -0.663, P = 0.508). Through ROC curves, the AUC for the percentage changes of LD, T2WI-CNR and ADC after two weeks of therapy were 0.756, 0.552 and 0.881, respectively, in the early prediction of the responses. Taking %ΔADC ≥ 15% to predict GoodR, the PPV was 87.5% (28/32). Taking %ΔADC ≤ 1% to predict PoorR, the NPV was 85.7% (12/14).

The percentage change of the ADC after two weeks of therapy outperforms T2WI-CNR and longest diameter in the early response prediction of GIST to targeted therapy.

This patient-based study proved ADC has good performance in the early prediction of response of GIST to targeted therapy, which may provide surrogate biomarker for the personalized treatment of GIST.

Tang, L, Sun, Y, Li, Z, Zhang, X, Ji, J, Li, X, Shen, L, Comparison of MRI Parameters in the Early Response Prediction of Gastrointestinal Stromal Tumor to Targeted Therapy: A Patient-based Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14001118.html