Limitations of Fluorine 18 Fluoromisonidazole in Assessing Treatment-induced Tissue Hypoxia after Transcatheter Arterial Embolization of Hepatocellular Carcinoma: A Prospective Pilot Study

Abstract

Purpose: To determine the variance and correlation with tumor viability of fluorine 18 (18F) fluoromisonidazole (FMISO) uptake in hepatocellular carcinoma (HCC) prior to and after embolization treatment. Materials and Methods: In this single-arm, single-center, prospective pilot study between September 2016 and March 2017, participants with at least one tumor measuring 1.5 cm or larger with imaging or histologic findings diagnostic for HCC were enrolled (five men; mean age, 68 years; age range, 61–76 years). Participants underwent18F-FMISO PET/CT before and after bland embolization of HCC. A tumor-to-liver ratio (TLR) was calculated by using standardized uptake values of tumor and liver. The difference in mean TLR before and after treatment was compared by using a Wilcoxon rank sum test, and correlation between TLR and tumor viability was assessed by using the Spearman rank correlation coefficient. Results: Four participants with five tumors were included in the final analysis. The median tumor diameter was 3.2 cm (IQR, 3.0–3.9 cm). The median TLR before treatment was 0.97 (IQR, 0.88–0.98), with a variance of 0.02, and the median TLR after treatment was 0.85 (IQR, 0.79–1), with a variance of 0.01; both findings indicate a narrow range of18F-FMISO uptake in HCC. The Spearman rank correlation coefficient was 0.87, indicating a high correlation between change in TLR and nonviable tumor. Conclusion: Although there was a correlation between change in TLR and response to treatment, the low signal-to-noise ratio of 18 F-FMISO in the liver limited its use in HCC.