A prospective evaluation of ¹⁸F-FDG and ¹¹C-acetate PET/CT for detection of primary and metastatic hepatocellular carcinoma

Because ¹⁸F-FDG PET has insufficient sensitivity for the detection of hepatocellular carcinoma (HCC), ¹¹C-acetate PET has been proposed as another technique for this use. We prospectively evaluated the value of PET/CT using these 2 tracers for the detection of primary and metastatic HCC. Methods: One hundred twelve patients (99 with HCC, 13 with cholangiocellular carcinoma) underwent biopsy and ¹⁸F-FDG and ¹¹C-acetate PET/CT. Results: The overall sensitivities of ¹⁸F-FDG, ¹¹C-acetate, and dual-tracer PET/CT in the detection of 110 lesions in 90 patients with primary HCC were 60.9%, 75.4%, and 82.7%, respectively. Elevated serum α-fetoprotein levels, an advanced tumor stage, portal vein tumor thrombosis, large tumors, and multiple tumors were significantly associated with positive ¹⁸F-FDG PET/CT results. Uptake of ¹¹C-acetate was associated with large and multiple tumors. For ¹⁸F-FDG, the sensitivities according to tumor size (1-2, 2-5, and ≥5 cm) were 27.2%, 47.8%, and 92.8%, respectively; for ¹¹C- acetate, these respective values were 31.8%, 78.2%, and 95.2%. ¹⁸F-FDG was more sensitive in the detection of poorly differentiated HCC. Overall survival was lower in patients with ¹⁸F-FDG PET/CT positive for all indexed lesions than in those with FDG negative or partially positive through the entire follow-up period. In analysis based on biopsied lesions, the sensitivity of ¹⁸F-FDG PET/CT was 64.4% for primary HCC and 84.4% for ¹¹C-acetate PET/CT. The overall sensitivities of ¹⁸F-FDG, ¹¹C-acetate, and dual-tracer PET/CT for 35 metastatic HCCs were 85.7%, 77.0%, and 85.7%, respectively. There was no significant difference in the sensitivity of tracers according to metastatic tumor size, location, or differentiation. Conclusion: The addition of ¹¹C-acetate to ¹⁸F-FDG PET/CT increases the overall sensitivity for the detection of primary HCC but not for the detection of extrahepatic metastases. ¹⁸F-FDG, ¹¹C-acetate, and dual-tracer PET/CT have a low sensitivity for the detection of small primary HCC, but ¹⁸F-FDG PET/CT has a relatively high sensitivity for the detection of extrahepatic metastases of HCC.