Oral 4.02: Dynamic contrast-enhanced MR imaging in risk stratification of thymic epithelial tumors

Background: To evaluate the diagnostic performance of dynamic contrast-enhanced MR imaging (DCE-MRI) in risk stratification of thymic epithelial tumors.

Methods: Ninety-three patients with suspected thymic masses were prospectively included in the study to undergo DCE-MRI prior to surgery or biopsy. The time-intensity curves (TICs) were categorized with type I (with a slow, continuous increase), type II (with a plateau form), and type III (with a gradual decrease). The semi-quantitative parameters, including relative enhancement, maximum enhancement (ME), maximum relative enhancement, time-of-arrival, time-to-peak (TTP), wash-in rate, wash-out rate, and brevity of enhancement, were analyzed among the tumors.

Results: Thirty-eight low-risk thymomas, 34 high-risk thymomas, and 21 thymic carcinomas were revealed pathologically. Type II TICs were predominantly observed in high-risk thymomas (85.3%) and thymic carcinomas (100%), while type III TICs was mainly seen in low-risk thymomas (57.9%) (P=0.000). The mean RE of thymic carcinomas (190.35%±94.3%) was higher than that of high-risk thymomas (136.5%±55.7%) (P=0.044). The mean MEs of thymic carcinomas (1,236.1%±389.1%) and low-risk thymomas (1,169.1%±489.9%) were significantly higher than that of high-risk thymomas (928.2%±314.1%) (P=0.012), respectively. The mean MRE of thymic carcinomas (228.1%±99.5%) was higher than those of high-risk thymomas (163.4%±56.7%) (P=0.016). The TTP of low-risk thymomas (126.9±54.8 L/s) was the earliest, then were those of high-risk thymomas (170.6±48.2 L/s) and thymic carcinomas (185.9±33.3 L/s) (P=0.000). The WIR of low-risk thymomas (45.2±30.7 L/s) was the fastest, then were those of thymic carcinomas (35.6±17.5 L/s) and high-risk thymomas (25.4±8.3 L/s) (P=0.001). The cutoff RE and MRE to differentiate high-risk thymomas from thymic carcinomas were 154.1% (sensitivity, 69.4%; specificity, 78.9%; and AUC, 0.680) and 175.2% (sensitivity, 76.2%; specificity, 61.1%; and AUC, 0.688), respectively. The cutoff ME to differentiate high-risk thymomas from thymic carcinomas and low-risk thymomas were 951.6% (sensitivity, 81.0%; specificity, 51.4%; and AUC, 0.661).

Conclusions: According to the type of TICs and dynamic indices, DCE-MRI is of value in predicting low-risk thymomas, high-risk thymomas, and thymic carcinomas.

Keywords: Dynamic contrast-enhanced MR imaging (DCE-MRI); thymic epithelial tumors; stratification