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Background: Immune checkpoint inhibitors (ICIs) have significantly improved survival in advanced melanoma. There is a need for robust biomarkers to identify patients who do not respond. We analysed 14 baseline 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) metrics and their evolution to assess their correlation with patient outcome, compared with 7 established biological markers and 7 clinical variables. Methods: We conducted a retrospective monocentric observational study of 29 patients with advanced melanoma who underwent baseline 18F-FDG PET/CT, followed by an early monitoring PET/CT (iPET) scan after 1 month of treatment and follow-up studies at 3rd (M3PET) and 6th month (M6PET). 18F-FDG uptake in immune organs (spleen, bone marrow, ileocecal valve) and derived spleen-to-liver (SLR) and bone-to-liver (BLR) ratios were reviewed by two PET readers for reproducibility analysis purposes including 14 PET variables. The most reproducible indexes were used for evaluation as predictors of overall survival (OS) in comparison with PET response using imPERCIST5, whole-body metabolic active tumour volume (WB-MATV) and biological parameters (lactate dehydrogenases (LDH), reactive protein c (CRP), white blood count (WBC), absolute lymphocyte count (ALC), neutrophil to lymphocyte ratio (NLR) and derived neutrophils to lymphocyte ratio). Results: Strong reproducibility's (intraclass coefficients of correlation (ICC) > 0.90) were observed for spleen anterior SUVpeak, spleen MV, spleen TLG, spleen length and BLRmean. ICC for SLRmean and ileocecal SUVmean were 0.86 and 0.65, respectively. In the 1-year OS 1 group, SLRmean tended to increase at each time point to reach a significant difference at M6-PET (p = 0.019). The same trends were observed with spleen SUVpeak anterior and spleen length. In the 1-year OS 0 group, a significative increase of spleen length was found at iPET, as compared with baseline PET (p = 0.014) and M3-PET (p = 0.0239). Univariable Kaplan-Meier survival analysis found that i%var spleen length, M3%var SLRmean, baseline LDH, i%var NLR and response at M6PET were all predictors of 1-year OS. Conclusions: SLRmean is recommended as a prognosticator in melanoma patients under immunotherapy: its increase greater than 25% at 3 months, compared with baseline, was associated with poor outcome after ICIs. [ABSTRACT FROM AUTHOR]

PurposeWe assessed whether imaging αvβ3 integrin could distinguish mature teratoma from necrosis in human non-seminomatous germ cell tumour (NSGCT) post-chemotherapy residual masses.MethodsHuman embryonal carcinoma xenografts (six/rat) were untreated (controls) or treated to form mature teratomas with low-dose cisplatin and all-trans retinoic acid (ATRA) over a period of 8 weeks. In another group, necrosis was induced in xenografts with high-dose cisplatin plus etoposide (two cycles).18F-Fluorodeoxyglucose (18F-FDG) small animal positron emission tomography (SA PET) imaging was performed in three rats (one control and two treated for 4 and 8 weeks with cisplatin+ATRA). Imaging of αvβ3 expression was performed in six rats bearing mature teratomas and two rats with necrotic lesions on a microSPECT/CT device after injection of the tracer [99mTc]HYNIC-RGD [6-hydrazinonicotinic acid conjugated to cyclo(Arg-Gly-Asp-D-Phe-Lys)]. Correlative immunohistochemistry studies of human and mouse αvβ3 expression were performed.ResultsCisplatin+ATRA induced differentiation of the xenografts. After 8 weeks, some glandular structures and mesenchymal cells were visible; in contrast, control tumours showed undifferentiated tissues. SA PET imaging showed that mature teratoma had very low avidity for 18F-FDG [mean standardised uptake value (SUVmean) = 0.48 ± 0.05] compared to untreated embryonal carcinoma (SUVmean = 0.92 ± 0.13) (p = 0.005). αvβ3 imaging accurately distinguished mature teratoma (tumour to muscle ratio = 4.29 ± 1.57) from necrosis (tumour to muscle ratio = 1.3 ± 0.26) (p = 0.0002). Immunohistochemistry studies showed that αvβ3 integrin expression was strong in the glandular structures of mature teratoma lesions and negative in host stroma.ConclusionImaging αvβ3 integrin accurately distinguished mature teratoma from necrosis following cisplatin-based treatment in human NSGCT xenografts. [ABSTRACT FROM AUTHOR]

Purpose: To seek for the minimal duration per bed position with a digital PET system without compromising image quality and lesion detection in patients requiring fast 18F-FDG PET imaging.Materials and Methods: 19 cancer patients experiencing pain or dyspnea and 9 pediatric patients were scanned on a Vereos system. List mode data were reconstructed with decreasing time frame down to 10 s per bed position. Noise was evaluated in the liver, blood pool and muscle, and using target-to-background ratios. Five PET readers recorded image quality, number of clinically relevant foci and of involved anatomical sites in reconstructions ranging from 60 to 10 s per bed position, compared to the standard 90 s reconstruction.Results: The following reconstructions, which harboured a noise not significantly higher than that of the standard reconstruction, were selected for clinical evaluation: 1iterations/10 subsets/20sec (1i10 s20sec), 1i10 s30sec, and 2i10 sPSF60sec. Only the 60 s per bed acquisition displayed similar target-to-background ratios compared to the standard reconstruction, but mean ratios were still higher than 2.0 for the 30 s reconstruction. Inter-rater agreement for the number of involved anatomical sites and detected lesion was good or almost perfect (Kappa: 0.64-0.91) for all acquisitions. In particular, kappa for the 30 s per bed acquisition was 0.78 and 0.91 for lesion and anatomical sites number, respectively. Intra-rater agreement was also excellent for the 30 s reconstruction (kappa = 0.72). Median estimated total PET acquisition time for the 1i10 s30sec, and the standard reconstruction were 4 and 12 min, respectively.Conclusions: Fast imaging is feasible with state-of-the-art PET systems. Acquisitions of 30 s per bed position are feasible with the Vereos system, requiring optimization of reconstruction parameters. [ABSTRACT FROM AUTHOR]

Aims: (1) To perform a comprehensive analysis of the time elapsed between the last G-CSF injection and the PET/CT examination on the biodistribution of 18F-FDG, with emphasis on liver, spleen, and bone marrow uptake, and (2) to investigate whether an inversion of the liver to spleen ratio affects the Deauville scoring. Materials and methods: Retrospectively included were 74 consecutive diffuse large B cell lymphoma (DLBCL) patients referred for baseline and interim examinations and receiving immunochemotherapy with various G-CSF regimens. A comprehensive evaluation considering baseline metabolic active tumour volume (MATV), factors affecting liver uptake, the type of G-CSF, and the time elapsed between chemotherapy/G-CSF and interim PET/CTs was performed. Results: Mean (± SD) percentage variations between baseline and interim PET/CTs (i-PET/CT) for bone marrow (%Variation_BONE), liver (%Variation_LIVER) and spleen (%Variation_SPLEEN) were equal to 32.0 ± 46.9%, 16.1 ± 42.8%, and 10.6 ± 51.1 %, respectively. %Variation_LIVER and %Variation_SPLEEN were higher in patients using lenograstim, but this was linked to lower uptakes at baseline and was therefore likely not due to G-CSF itself. The mean delay between G-CSF injection and i-PET/CT acquisition was not an independent explanatory variable for %Variation_BONE, %Variation_LIVER, and %Variation_SPLEEN. On the contrary, %Variation_BONE and %Variation_SPLEEN were negatively correlated to the time-lapse between the end of chemotherapy and i-PET/CT: ρ = − 0.342 (p = 0.010) and ρ = − 0.529 (p < 0.0001), respectively. Patients with a time-lapse since the last injection of chemotherapy < 17 days displayed higher bone and spleen SUVmaxEARL. %Variation_LIVER was positively correlated to baseline MATV: ρ = 0.243 (p = 0.039). Patients displaying a high baseline MATV ≥ 177 cc had significantly lower liver SUVmaxEARL at baseline. This difference was no longer observed at i-PET/CT, after tumours had shrunk. Conclusions: Neither the type of G-CSF used nor the time elapsed between its last injection and i-PET/CT examination independently influences bone, hepatic, or splenic uptakes at i-PET/CT. The major determinant for the occurrence of a bone or spleen hypermetabolism on i-PET/CT is the time elapsed between the chemotherapy and the examination, which should be maintained above 15 days. Inversion of the liver to spleen ratio appeared to be due to increased spleen hypermetabolism on i-PET/CT, making unlikely an impact on the Deauville scoring. [ABSTRACT FROM AUTHOR]