Background:68Ga-Prostate Specific Membrane
Antigen (68Ga-PSMA), a positron emission tomography (PET) tracer that was recently introduce for imaging of
prostate cancer, may accumulate in other solid
tumors including
Hepatocellular Carcinoma (HCC). The aim of the study was to assess the potential role of
68Ga-PSMA PET-Computed Tomography (CT) for imaging of HCC. Material and Methods: A prospective pilot study in seven patients with HCC with 41 liver lesions: 37 suspected malignant lesions (
tumor lesions) and 4 regenerative nodules. For each liver lesion, uptake of
68Ga-PSMA and
18F-FDG uptake were measured [standard uptake value (SUV) and lesion-to-liver background ratios (TBR-SUV)], and correlated with dynamic characteristics (HU and TBR-HU) obtained on contrast enhanced CT data. Immunohistochemistry staining of PSMA in the
tumor tissue was analyzed in samples obtained from 5 patients with HCC and compared to control samples from 3 patients with
prostate cancer. Results: Thirty-six of the 37
tumor lesions and none of the regenerative nodules showed increased
68Ga-PSMA uptake while only 10 lesions were
18F-FDG avid. Based on contrast enhancement,
tumor lesions were categorized into 27 homogeneously enhancing lesions, nine lesions with "mosaic" enhancement composed of enhancing and non-enhancing regions in the same lesion and a single non-enhancing lesion, the latter being the only non-68Ga-PSMA avid lesion. Using the Mann-Whitney test,
68Ga-PSMA uptake was found significantly higher in enhancing
tumor areas compared to non-enhancing areas and in contrast,
18F-FDG uptake was higher in non-enhancing areas, P<0.001 for both.
68Ga-PSMA uptake (TBR SUVmax) was found to correlate with vascularity (TBR-HU) (Spearman r=0.866, p<0.001). Immunohistochemistry showed intense intra-tumoral microvessel staining for PSMA in HCC, in contrast with cytoplasmic and membranous staining, mainly in the
luminal border, in
prostate cancer samples. In two of the study patients
68Ga-PSMA PET-CT identified unexpected extrahepatic
metastases. Four regenerative liver nodules showed no increased uptake of either of the PET tracers. Conclusion:68Ga-PSMA PET-CT is superior to
18F-FDG PET-CT in imaging patients with HCC. HCC lesions are more commonly hypervascular taking up
68Ga-PSMA in tumoral micro-vessels.
68Ga-PSMA PET-CT is a potential novel modality for imaging patients with HCC.