Diffusion-weighted imaging for identifying patients at high risk of tumor recurrence following liver transplantation.

Background: Tumor recurrence is the major risk factor affecting post-transplant survival. In this retrospective study, we evaluate the prognostic values of magnetic resonance (MR) diffusion-weighted imaging (DWI) in liver transplantation for hepatocellular carcinoma (HCC).
Methods: From April 2014 to September 2016, 106 HCC patients receiving living donor liver transplantation (LDLT) were enrolled. Nine patients were excluded due to postoperative death within 3 months and incomplete imaging data. The association between tumor recurrence, explant pathologic findings, and DWI parameters was analyzed (tumor-to-liver diffusion weighted imaging ratio, DWI _T/L ; apparent diffusion coefficients, ADC). The survival probability was calculated using the Kaplan-Meier method.
Results: Sixteen of 97 patients (16%) developed tumor recurrence during the follow-up period (median of 40.9 months; range 5.2-56.5). In those with no viable tumor (n = 65) on pretransplant imaging, recurrence occurred only in 5 (7.6%) patients. Low minimum ADC values (p = 0.001), unfavorable tumor histopathology (p <  0.001) and the presence of microvascular invasion (p <  0.001) were risk factors for tumor recurrence, while ADC _mean (p = 0.111) and DWI _T/L (p = 0.093) showed no significant difference between the groups. An ADC _min  ≤ 0.88 × 10 ^- 3  mm ² /s was an independent factor associated with worse three-year recurrence-free survival (94.4% vs. 23.8%) and overall survival rates (100% vs. 38.6%).
Conclusions: Quantitative measurement of ADC _min is a promising prognostic indicator for predicting tumor recurrence after liver transplantation.