ABSTRACT
Prostate-specific membrane antigen (PSMA) is a glycosylated type-II transmembrane protein highly expressed in certain tumor cells. To the best of our knowledge, this is the first case reported of an isolated well-differentiated hepatocellular carcinoma (HCC) strongly suspected on gallium-68 (68Ga)-PSMA positron emission tomography/computed tomography (PET/CT), which was not well characterized both on magnetic resonance imaging (MRI) liver with Primovist as well as fluorine-18 (18F)-choline PET/CT. Our patient had previous prostate cancer and previously was imaged using 18F-choline PET/CT. The last scan showed an indeterminate segment VII hypodensity which was not significantly choline-avid. The lesion was initially stable on serial MRI scans but then showed growth from 1.0 to 1.5 cm. 68Ga-PSMA PET/CT was performed. The lesion was intensely tracer-avid. This was surgically excised and histology confirmed the presence of well-differentiated HCC. Well-differentiated HCC can be optimally imaged using 68Ga-PSMA PET/CT and further prospective studies are needed to look into the potential of this imaging modality.
ABSTRACT
UNLABELLED: Compliance with radiobiologic principles of radionuclide internal dosimetry is fundamental to the success of (90)Y radioembolization. The artery-specific SPECT/CT partition model is an image-guided personalized predictive dosimetric technique developed by our institution, integrating catheter-directed CT hepatic angiography (CTHA), (99m)Tc-macroaggregated albumin SPECT/CT, and partition modeling for unified dosimetry. Catheter-directed CTHA accurately delineates planning target volumes. SPECT/CT tomographically evaluates (99m)Tc-macroaggregated albumin hepatic biodistribution. The partition model is validated for (90)Y resin microspheres based on MIRD macrodosimetry. METHODS: This was a retrospective analysis of our early clinical outcomes for inoperable hepatocellular carcinoma. Mapping hepatic angiography was performed according to standard technique with the addition of catheter-directed CTHA. (99m)Tc-MAA planar scintigraphy was used for liver-to-lung shunt estimation, and SPECT/CT was used for liver dosimetry. Artery-specific SPECT/CT partition modeling was planned by experienced nuclear medicine physicians. RESULTS: From January to May 2011, 20 arterial territories were treated in 10 hepatocellular carcinoma patients. Median follow-up was 21 wk (95% confidence interval [CI], 12-50 wk). When analyzed strictly as brachytherapy, (90)Y radioembolization planned by predictive dosimetry achieved index tumor regression in 8 of 8 patients, with a median size decrease of 58% (95% CI, 40%-72%). Tumor thrombosis regressed or remained stable in 3 of 4 patients with baseline involvement. The best α-fetoprotein reduction ranged from 32% to 95%. Clinical success was achieved in 7 of 8 patients, including 2 by sublesional dosimetry, in 1 of whom there was radioembolization lobectomy intent. Median predicted mean radiation absorbed doses were 106 Gy (95% CI, 105-146 Gy) to tumor, 27 Gy (95% CI, 22-33 Gy) to nontumorous liver, and 2 Gy (95% CI, 1.3-7.3 Gy) to lungs. Across all patients, tumor, nontumorous liver, and lungs received predicted ≥91 Gy, ≤51 Gy, and ≤16 Gy, respectively, via at least 1 target arterial territory. No patients developed significant toxicities within 3 mo after radioembolization. The median time to best imaging response was 76 d (95% CI, 55-114 d). Median time to progression and overall survival were not reached. SPECT/CT-derived mean tumor-to-normal liver ratios varied widely across all planning target volumes (median, 5.4; 95% CI, 4.1-6.7), even within the same patient. CONCLUSION: Image-guided personalized predictive dosimetry by artery-specific SPECT/CT partition modeling achieves high clinical success rates for safe and effective (90)Y radioembolization.
