Risk of posttransplant hepatocellular carcinoma recurrence is greater in recipients with higher platelet counts in living donor liver transplantation.

Platelets interact with tumor cells and promote metastasis. The importance of platelets in posttransplant hepatocellular carcinoma (HCC) recurrence is unclear. Thus, we aimed to evaluate the association between preoperative platelet count (PLT) and HCC recurrence after living donor liver transplantation. Of 359 recipients of livers from living donors for HCC, 209 of 240 patients who had preoperative PLT ≤75 × 109 /L were matched with 97 of 119 patients who had preoperative PLT >75 × 109 /L using propensity score matching, with an unfixed matching ratio based on factors such as tumor biology. The cutoff value of 75 × 109 /L was set based on optimum stratification analysis. Survival analysis was performed with death as a competing risk event. The primary outcome was overall HCC recurrence. The median follow-up time was 59 months. Before matching, recurrence probability at 1, 2, and 5 years after transplantation was 4.7%, 9.2%, and 11.3% for the low platelet group and 14.5%, 23.0%, and 30.5% for the high platelet group. Recurrence risk was significantly greater in the high platelet group in both univariate (hazard ratio [HR] = 3.09; 95% confidence interval [CI], 1.86-5.14; P < 0.001) and multivariate analyses (HR = 2.10; 95% CI, 1.23-3.60; P =  0.007). In the matched analysis, recurrence risk was also greater in the high platelet group in both univariate (HR = 2.33; 95% CI, 1.36-4.01; P =  0.002) and multivariate analyses (HR = 1.90; 95% CI, 1.02-3.54; P =  0.04). Preoperative PLT had no interaction with the Milan criteria, alpha-fetoprotein level, Edmonson grade, microvascular invasion, or intrahepatic metastasis. Incorporation of preoperative PLT into the Milan criteria significantly improved predictive power. Inflammation-based scores including neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and the inflammation-based index did not show superiority to preoperative PLT in predicting HCC recurrence. In conclusion, preoperative PLT appears to be an important host factor affecting HCC recurrence after living donor liver transplantation. Liver Transplantation 24 44-55 2018 AASLD.