Role of 11C-acetate and 18F FDG dual tracer PET-CT scan for detection of hepatocellular carcinoma

Abstract

PURPOSE: Up to 45% of Hepatocellular Carcinoma (HCC) show atypical contrast enhancement (CE) pattern on CT/MR, thereby requiring histologic confirmation. The aim of this study is to evaluate the additional value of Dual Tracer (DT) PET with 11C Acetate (Ac) and 18F FDG for detection and characterization of HCC. MATERIAL & METHOD: Consecutive patients who had histological confirmation of HCC and underwent CT/MR and DT in our centres from 2014-16 were identified. CE and PET uptake patterns were reviewed. Typical CE pattern on CT/MR was arterial hyper-enhancement followed by portovenous/delayed phase washout. All other CE patterns were considered atypical. On PET, a lesion was deemed positive by visual inspection of lesion above background liver uptake on Ac and/or FDG. Results were compared with tumor size and grade on histology. Tumour size were separated into <3 cm, 3-5 cm and >5 cm groups as each has different treatment option. Grading was based on Edmondson and Steiner system. Pearson’s Chi-Square tests were applied to compare the sensitivities and ANOVA-test for subgroup analysis. RESULTS: Thirty-two HCC lesions from 24 patients were identified (mean size SD 34 27 mm). The sensitivity of CT/MR by CE pattern was 53%, FDG alone 56%, Ac alone 94%, DT 97% and combined CT/MR with DT 100% (p<0.0001). Two lesions were non-Ac avid. Enhancement pattern were not affected by tumour size whereas FDG sensitivities increase with tumour size from 39% to 67% and 75% for lesions <3 cm, 3-5 cm and >5cm respectively. Histological grade available in 30 lesions were well differentiated HCC (n=7), moderately-differentiated HCC (n=22) and poorly differentiated HCC (n=1). Atypical enhancement pattern was more common in well-differentiated compared to moderately-differentiated lesions (71% vs 45%). No trend was observed for tracer avidities in different grades of HCC. CONCLUSION: DT combined with CT/MR increases the sensitivity of HCC detection compared to CT/MR alone, providing 100% sensitivity and hence, being most helpful in equivocal liver lesions with atypical contrast enhancement. CLINICAL RELEVANCE: The use of DT obviates tissue sampling for diagnosing HCC in patients with liver lesions with atypical CT/MR contrast enhancement.