Radioembolization with 90Y glass microspheres for hepatocellular carcinoma: significance of pretreatment 11C-acetate and 18F-FDG PET/CT and posttreatment 90Y PET/CT in individualized dose prescription.

PURPOSE: The aim of this study was to establish an algorithm for the prescription of 90Y glass microsphere radioembolization (90Y-GMRE) of HCC in individual patients based on the relationship between tumour dose (TD) and response validated by 90Y PET/CT dosimetry and dual-tracer PET/CT metabolic parameters. METHODS: The study group comprised 62 HCC patients prospectively recruited for 90Y-GMRE who underwent pretreatment dual-tracer (11C-acetate and 18F-FDG) PET/CT as surrogate markers of HCC cellular differentiation. Pretreatment tumour-to-nontumour ratio on 99mTc-MAA SPECT/CT (T/NTMAA) was correlated with posttreatment 90Y PET/CT T/NT90Y after quantification validation. The TD-response relationship for HCC of different tracer groups was assessed on follow-up PET/CT 2 months after treatment. RESULTS: 90Y PET/CT was accurate in the measurement of recovery of injected 90Y activity (81.9-99.9%, median 94.8%). Pretreatment SPECT/CT T/NTMAA was strongly correlated with posttreatment 90Y PET/CT T/NT90Y (5.6 ± 3.2 versus 5.9 ± 3.5, T/NT90Y 1.01 × T/NTMAA + 0.161, r = 0.918, P < 0.05). The response rates were 72.4% (21/29), 70.6% (12/17) and 25% (4/16) for well, moderately and poorly differentiated HCC, respectively. The cut-off TD for a good response was significantly different between poorly differentiated and well/moderately differentiated HCC (262 Gy versus 152/174 Gy) with 89.2% sensitivity and 88% specificity. At a limiting tolerated liver dose of 70 Gy, the T/NTMAA thresholds for predicting a good response in poorly differentiated and well/moderately differentiated HCC were 3.5 and 2.0/2.3. Disregarding HCC cellular differentiation, the cut-off TD became 170 Gy, with lower sensitivity (70.3%) and specificity (76%). CONCLUSION: 90Y PET/CT can provide accurate dosimetry for 90Y-GMRE. Pretreatment T/NTMAA predicts posttreatment T/NT90Y. The TD thresholds for a good response are tracer-dependent, with a strong correlation between HCC radiosensitivity and cellular differentiation and other PET-based parameters. These cytokinetic factors improve treatment efficacy while minimizing organ damage for the prescription of personalized 90Y-GMRE.

11C-Acetate Positron Emission Tomography for Detection of Occult Metastatic Recurrence in Hepatoblastoma.

Hepatoblastoma is the most common primary liver cancer in the pediatric population. Disease relapse might be occult and difficult to detect. C-acetate positron emission tomography has been applied in patients with hepatocellular carcinoma due to the insensitivity of fluorodeoxyglucose, but data on hepatoblastoma patients have been scarce. We describe the use of C-acetate positron emission tomography/computed tomography scan as a sensitive method in the identification of an occult bony metastatic recurrence in a 6-year-old girl with a history of hepatoblastoma treated with chemotherapy.

Outcome of hepatobiliary scanning: preterm versus full-term cholestatic infants.

OBJECTIVES: The aims of this study were to evaluate the specificity of a non-draining hepatobiliary scintigraphy (HBS) for biliary atresia (BA) in preterm and full-term babies, to verify the relationship between non-draining scan and higher levels of direct bilirubin and to find an objective criterion to guide the time in performing HBS. METHODS: A total of 175 infants (113 males and 62 females, median age of 45 days) with 181 HBS performed in Tuen Mun Hospital between January 1998 and May 2010 were retrospectively analysed. A 'non-draining' scan was defined as one showing no excretion of radiolabelled tracer into the small bowel 24 h after injection. The disease category, epidemiological and laboratory data were compared between infants having non-draining and draining scans. In addition, the predictive value of a negative scan for BA was compared between preterm and full-term infants. RESULTS: Twenty infants (11.4%) were surgically confirmed to have BA. A non-draining scan was found to be 100% sensitive for BA, and the specificity was 96% and 78% among full-term infants and preterm infants, respectively. The mean direct bilirubin values of infants with BA and intrahepatic cholestasis were 141.9 and 111.3 µmol/L, respectively, which were significantly higher than 67.2 µmol/L seen in infants with draining scans. This analysis shows that using direct bilirubin ≥63 µmol/L as an objective criterion in guiding the time to perform HBS is most cost-effective. CONCLUSION: Our data supported that using direct bilirubin ≥63 µmol/L as an objective criterion in guiding the time to perform HBS will avoid unnecessary scans.

68Ga-DOTATOC and 68Ga-PSMA PET/CT Unmasked a Case of Prostate Cancer With Neuroendocrine Differentiation.

A bedridden 90-year-old man with fever and elevated prostate-specific antigen (PSA) (49 ng/mL) was referred for differentiation between infection and tumor. F-FDG PET/CT was negative for infection, but Ga-PSMA PET/CT showed multiple lesions in prostate gland with infiltration to bladder wall and seminal vesicle, consistent with locally advanced prostate cancer. The lesion with the highest Ga-PSMA uptake was strongly avid for Ga-DOTATOC, suggesting neuroendocrine tumor differentiation. After hormonal therapy, PSA normalized, but chromogranin-A increased (from 251 to 398 ng/mL), inferring progression of neuroendocrine tumor differentiation. Advanced prostate cancer may require investigation for pathological neuroendocrine transformation, although PSA may suggest improvement.

11C-acetate PET/CT for metabolic characterization of multiple myeloma: a comparative study with 18F-FDG PET/CT.

UNLABELLED: We prospectively compared (11)C-acetate with (18)F-FDG in a PET/CT evaluation of multiple myeloma (MM), specifically on diagnostic accuracy, identification of high-risk patients, and monitoring of treatment response. METHODS: Dual-tracer PET/CT was performed on 35 pathologically and clinically confirmed and untreated patients (26 with symptomatic MM, 5 with smoldering MM, and 4 with monoclonal gammopathy of unknown significance) and 20 individuals with normal marrow. RESULTS: (11)C-acetate showed significant incremental value over (18)F-FDG (84.6% vs. 57.7%) for positively identifying patients with diffuse and focal symptomatic MM, and was negative in patients with indolent smoldering MM and monoclonal gammopathy of unknown significance. Three functional parameters-number of (11)C-acetate-avid and (18)F-FDG-avid focal bone lesions and (11)C-acetate general marrow activity-strongly correlated with ß-2-microglobulin as surrogate imaging markers of tumor burden. After induction chemotherapy, the metabolic change in (11)C-acetate general marrow activity correlated with clinical response. CONCLUSION: Metabolic characterization of MM in diagnosis, risk stratification, and treatment monitoring can be done more accurately by assessing lipid metabolism with (11)C-acetate than by assessing glucose metabolism with (18)F-FDG.

Dual-tracer PET/CT in renal angiomyolipoma and subtypes of renal cell carcinoma.

UNLABELLED: We studied the metabolic characteristics of RCC subtypes and angiomyolipoma with 18F-FDG and 11C-acetate PET/CT. METHODS: Fifty-eight patients with both baseline CT and dual-tracer PET/CT were recruited: 10 angiomyolipoma (16 lesions) and 48 RCC (50 lesions). Each lesion was assessed for SUVmax ratio (lesion-to-normal kidney) on 11C-acetate/18F-FDG PET and attenuation density on CT. Receiver operating characteristic (ROC) curve was analyzed to define the threshold of 11C-acetate SUVmax ratio for differentiating angiomyolipoma from RCC. Thirty-nine RCC patients were selected for 3-year disease-free survival analysis. RESULTS: All angiomyolipoma showed negative 18F-FDG but markedly increased 11C-acetate metabolism, significantly higher than RCC (11C-acetate SUVmax ratio = 4.11 ± 0.53 vs 2.00 ± 0.71; P < 0.05). 11C-acetate SUVmax ratio = 3.71 could differentiate angiomyolipoma including "fat-poor angiomyolipoma" (n = 10) from RCC with sensitivity of 93.8% (15/16) and specificity of 98.0% (49/50). Different RCC subtypes/grades (25 low- and 11 high-grade clear cell [CC], 7 chromophobe, 4 papillary, and 1 collecting duct) were found to have different dual-tracer metabolic pattern (P < 0.05), with overall RCC detection sensitivity of 90% (45/50). All chromophobe RCC were avid only for C-acetate but not 18F-FDG, whereas papillary RCC were primarily the opposite. RCC-CC showed variable dual-tracer uptake: high-grade more avid for F-FDG, low-grade more for 11C-acetate. Four RCC cases negative by dual-tracers were of low-grade RCC-CC. "Primary RCC being 18F-FDG-avid" was the only independent predictor of RCC recurrence in 3 years (P < 0.05), with a median disease-free survival of 22 months. CONCLUSION: 11C-acetate PET/CT helps in differentiating "fat-poor angiomyolipoma" from RCC. Dual-tracer PET/CT has value in diagnosis of RCC subtypes and predicting survival.

Segmental renal artery stenosis diagnosed with captopril renography in a child.

A 9-year-old girl with clinical suspicion of renovascular hypertension was referred for captopril renography. This showed a segmental abnormality when the left kidney was analyzed as two separate cortical regions of interest. Subsequent angiography confirmed stenosis in the distal mid and lower pole branches of the left renal artery.