Volume 128, Issue 7, Pages 1787-1795 (June 2005) Positron Emission Tomography Imaging of Adenoviral-Mediated Transgene Expression in Liver Cancer Patients  Iván Peñuelas, Guillermo Mazzolini, José F. Boán, Bruno Sangro, Josep Martí-Climent, María Ruiz, Juan Ruiz, Nagichettiar Satyamurthy, Cheng Qian, Jorge R. Barrio, Michael E. Phelps, José A. Richter, Sanjiv S. Gambhir, Jesús Prieto  Gastroenterology  Volume 128, Issue 7, Pages 1787-1795 (June 2005) DOI: 10.1053/j.gastro.2005.03.024 Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 1 PET-CT imaging of HSV1-tk transgene expression in humans. Columns 1 to 3 show the 5-mm-thick coronal, sagittal, and transaxial slices, respectively, from a [18F]FHBG-PET-CT study in patient 5. All sections are centered on the treated tumor lesion (dotted lines in the CT images) and show [18F]FHBG accumulation at the tumor site (arrows). Anatomic-metabolic correlation can be obtained by fused PET-CT imaging. The white spots on the liver seen on the CT images correspond to lipiodol (arrowheads) retention after transarterial embolization of the tumor and a transjugular intrahepatic portosystemic shunt (★). Tracer signal can be seen in the treated lesion (arrows), whereas no specific accumulation of the tracer can be seen in the necrotic, lipiodol-retaining regions around it. H, heart; L, liver; LB, large bowel; RL, right lung; Sp, spleen. Gastroenterology 2005 128, 1787-1795DOI: (10.1053/j.gastro.2005.03.024) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 2 Viral dose-dependent imaging of HSV1-tk transgene expression in patients. Transaxial magnetic resonance images show the treated tumor nodules (white arrows) and the corresponding [18F]FHBG-PET images obtained 60 minutes after injection of [18F]FHBG for 2 patients enrolled in 2 consecutive adenoviral dose steps: patient 3 (2 × 1011 vp) (A) and patient 4 (1012 vp) (B). Specific [18F]FHBG accumulation can be seen only in (B) (black arrows). Two foci are clearly identified because the adenoviral vector was injected in 2 different sites inside the tumor lesion. However, no significant accumulation is evident in the treated nodule in (A). In this case, diffuse accumulation of the tracer in nontumoral hepatic tissue shows metabolic clearance of the tracer, whereas absent metabolism of the tracer in the tumor probably reflects cellular changes leading to dedifferentiation and loss of hepatocyte phenotype. Late images (up to 6.5 hours) also did not show accumulation in the lesion in this case. L, liver; Sp, spleen; St, stomach. Gastroenterology 2005 128, 1787-1795DOI: (10.1053/j.gastro.2005.03.024) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 3 Higher vector titers do not necessarily produce higher transgene expression in the tumor, as evidenced by [18F]FHBG accumulation. Coronal [18F]FHBG-PET images obtained from patient 4 (1012 vp) (A) and patient 6 (2 × 1012 vp) (B) starting 1.5 and 6.5 hours after injection of the tracer are shown. For the patient treated with the lower adenoviral vector dose, specific [18F]FHBG accumulation in the treated lesion can readily be ascertained in the early images (arrow), but it can be seen only 6.5 hours after injection for the patient treated with the higher dose (arrow). Furthermore, whole-body images do not show specific accumulation of [18F]FHBG in any other site. At later times, the tracer accumulates in the bladder (b) and the intestines (i) because of physiological elimination. Gastroenterology 2005 128, 1787-1795DOI: (10.1053/j.gastro.2005.03.024) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 4 Time course of [18F]FHBG accumulation: relationship to viral dose. Graphs shown in (A) and (B) illustrate the time course of SUV in 2 different areas of the liver: the treated tumor lesion (■) and the nontumoral parenchyma represented by the mean value of 5 unrelated liver regions of interest (ROIs) ± SD (▵). For patient 2 (1011 vp) (A), the 2 curves depict a similar pattern for both regions, whereas a clear difference between them can be perceived for patient 5 (1012 vp) (B). (C) Ratio between the radioactivity concentration in the treated tumor and in the nontumoral liver parenchyma as a function of time after injection of [18F]FHBG. A representative case from each cohort of patients is shown. SUV ratio values were calculated for each patient by using the same kind of ROIs as in (A) and (B). After minute 40, ratios were ≤1 for the 3 lower doses: 2 × 1010 (○), 1011 (□), and 2 × 1011 (▵) vp. Conversely, for vector doses of 1012 (■) and 2 × 1012 (♦) vp, radioactivity was concentrated in the treated lesion, probably because of HSV1-tk expression. Error bars show the error associated with the SUV ratios, which were calculated by using the theory of error propagation. Gastroenterology 2005 128, 1787-1795DOI: (10.1053/j.gastro.2005.03.024) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 5 Monitoring of HSV1-tk transgene expression time variation by PET. Coronal [18F]FHBG-PET images obtained 2 and 9 days after the first dose of AdCMVtk and 2 days after readministration (day 30) of the adenoviral vector on the same lesion are shown. Specific [18F]FHBG accumulation in the treated tumor can be seen only at day 2 (arrow), and no specific accumulation can be seen either at day 9 or in the re-treatment. Radioactivity can be observed in all cases in the intestine (i) and the bladder (b) as a result of physiological clearance of the tracer. Late images obtained up to 6.5 hours after injection did not show specific tracer accumulation in the lesion either on day 9 or in the re-treatment study (not shown). Gastroenterology 2005 128, 1787-1795DOI: (10.1053/j.gastro.2005.03.024) Copyright © 2005 American Gastroenterological Association Terms and Conditions