11C-Acetate and 18F-FDG PET/CT for Clinical Staging and Selection of Patients with Hepatocellular Carcinoma for Liver Transplantation on the Basis of Milan Criteria: Surgeon's Perspective

The success of liver transplantation (LT) for hepatocellular carcinoma (HCC) is enhanced by careful patient selection on the basis of the Milan criteria. The criteria are traditionally assessed by contrast CT, which is known to be affected by structural or architectural changes in cirrhotic livers. We aimed to compare dual-tracer (C-11-acetate and F-18-FDG) PET/CT with contrast CT for patient selection on the basis of the Milan criteria. Methods: Patients who had HCC and had undergone both preoperative dual-tracer PET/CT and contrast CT within a 1-mo interval were retrospectively studied. They then underwent either LT (n = 22) or partial hepatectomy (PH) (n = 21; HCC of <= 8 cm). Imaging data were compared with data from postoperative pathologic analysis for accuracy in assessment of parameters specified by the Milan criteria (tumor size and extent, vascular invasion, and metastasis), TNM staging, and patient selection for LT. Results: Dual-tracer PET/CT performed equally well in both LT and PH groups for HCC detection (94.1% vs. 95.8%) and TNM staging (90.9% vs. 90.5%). Contrast CT performed reasonably well in the LT group but not in the PH group for HCC detection (67.6% vs. 37.5%) and TNM staging (54.5% vs. 28.6%). In the LT group, the sensitivity and specificity of contrast CT for patient selection on the basis of the Milan criteria were 43.8% and 66.7%, respectively (comparable to values in the literature); the sensitivity and specificity of dual-tracer PET/CT were 93.8% and 100%, respectively (both Ps < 0.05). From the surgeon's perspective, we tended to perform transplantation for patients with higher diagnostic certainty (stricter CT criteria) because of a shortage of donor grafts. Patients who were not transplant candidates usually underwent up-front hepatectomy without the benefit of reassessment contrast CT, resulting in lower accuracies for the PH group. The overall sensitivity (96.8%) and specificity (91.7%) of dual-tracer PET/CT for patient selection for LT were significantly higher than those of contrast CT (41.9% and 33.0%, respectively) (both Ps < 0.05). Sources of error for contrast CT were related to cirrhosis or previous treatment and included difficulty in differentiating cirrhotic nodules from HCC (39%) and estimation of tumor size (14%). Overstaging of vascular invasion (4.6%) and extrahepatic metastases (4.6%) was infrequent. The rate of false-negative results of dual-tracer PET/CT was 4.7%. Conclusion: Dual-tracer PET/CT was significantly less affected by cirrhotic changes than contrast CT for HCC staging and patient selection for LT on the basis of the Milan criteria. The inclusion of dual-tracer PET/CT in pretransplant workup may warrant serious consideration.