Purpose: Radiolabelled fibroblast activation protein inhibitors (FAPI) are promising molecular imaging tracers for the diagnosis and staging of pancreatobiliary cancer. To enable treatment response assessment with [⁶⁸Ga]Ga-FAPI-46, the day-to-day variability of its uptake must be defined. This study aimed to determine the repeatability of semi-quantitative [⁶⁸Ga]Ga-FAPI-46 PET/CT measurements in pancreatobiliary cancers. Methods: Patients with pathologically confirmed pancreatobiliary cancer (pancreatic ductal adenocarcinoma (PDAC) or cholangiocarcinoma (CCA)) were included. Patients underwent two [⁶⁸Ga]Ga-FAPI-46 PET/CT scans, within 7 days, without any treatment before or between scans. Static long axial field-of-view (LAFOV) PET/CT scans were performed 60 min post-injection of [⁶⁸Ga]Ga-FAPI-46 (EARL2-compliant reconstruction). Suspected malignant lesions were semi-automatically delineated (local background-adjusted 50% isocontour of the peak standardised uptake value (SUV)) and semi-quantitative measurements were extracted (SUV_mean, SUV_peak and SUV_max). Tumour-to-background ratios (TBR) were also calculated. Repeatability was assessed using the repeatability coefficient (RC) and the intraclass correlation coefficient (ICC). Results: Twelve patients were included (seven PDAC, three perihilar CCA and two intrahepatic CCA). The median injected dose was 216 MBq (interquartile range (IQR) 167–266 MBq) and the median uptake time was 60 min (range 60–68). In total, 70 FAPI-positive lesions were delineated. The RCs of SUV_mean, SUV_peak and SUV_max were 23.7%, 23.9% and 29.8%, respectively. For the blood pool adjusted TBR_mean, TBR_peak and TBR_max, the RC’s were 21.6%, 20.8% and 28.0%, respectively. All ICCs were above 0.98. Conclusion: Semi-quantitative measurements of [⁶⁸Ga]Ga-FAPI-46 PET/CT have an excellent repeatability and can potentially be used in future studies to assess treatment response in pancreatobiliary cancers.

Background: Preoperative planning of patients diagnosed with pancreatic head cancer is difficult and requires specific expertise. This pilot study assesses the added value of three-dimensional (3D) patient models and computer-aided detection (CAD) algorithms in determining the resectability of pancreatic head tumors. Methods: This study included 14 hepatopancreatobiliary experts from eight hospitals. The participants assessed three radiologically resectable and three radiologically borderline resectable cases in a simulated setting via crossover design. Groups were divided in controls (using a CT scan), a 3D group (using a CT scan and 3D models), and a CAD group (using a CT scan, 3D and CAD). For the perceived fulfillment of preoperative needs, the quality and confidence of clinical decision-making were evaluated. Results: A higher perceived ability to determine degrees and the length of tumor–vessel contact was reported in the CAD group compared to controls (p = 0.022 and p = 0.003, respectively). Lower degrees of tumor–vessel contact were predicted for radiologically borderline resectable tumors in the CAD group compared to controls (p = 0.037). Higher confidence levels were observed in predicting the need for vascular resection in the 3D group compared to controls (p = 0.033) for all cases combined. Conclusions: “CAD (including 3D) improved experts’ perceived ability to accurately assess vessel involvement and supports the development of evolving techniques that may enhance the diagnosis and treatment of pancreatic cancer”.

OBJECTIVE: In this pilot study, we investigated the feasibility of response prediction using digital [ 18 F]FDG PET/computed tomography (CT) and multiparametric MRI before, during, and after neoadjuvant chemoradiation therapy in locally advanced rectal cancer (LARC) patients and aimed to select the most promising imaging modalities and timepoints for further investigation in a larger trial. METHODS: Rectal cancer patients scheduled to undergo neoadjuvant chemoradiation therapy were prospectively included in this trial, and underwent multiparametric MRI and [ 18 F]FDG PET/CT before, 2 weeks into, and 6-8 weeks after chemoradiation therapy. Two groups were created based on pathological tumor regression grade, that is, good responders (TRG1-2) and poor responders (TRG3-5). Using binary logistic regression analysis with a cutoff value of P  ≤ 0.2, promising predictive features for response were selected. RESULTS: Nineteen patients were included. Of these, 5 were good responders, and 14 were poor responders. Patient characteristics of these groups were similar at baseline. Fifty-seven features were extracted, of which 13 were found to be promising predictors of response. Baseline [T2: volume, diffusion-weighted imaging (DWI): apparent diffusion coefficient (ADC) mean, DWI: difference entropy], early response (T2: volume change, DWI: ADC mean change) and end-of-treatment presurgical evaluation MRI (T2: gray level nonuniformity, DWI: inverse difference normalized, DWI: gray level nonuniformity normalized), as well as baseline (metabolic tumor volume, total lesion glycolysis) and early response PET/CT (Δ maximum standardized uptake value, Δ peak standardized uptake value corrected for lean body mass), were promising features. CONCLUSION: Both multiparametric MRI and [ 18 F]FDG PET/CT contain promising imaging features to predict response to neoadjuvant chemoradiotherapy in LARC patients. A future larger trial should investigate baseline, early response, and end-of-treatment presurgical evaluation MRI and baseline and early response PET/CT.

Near-infrared (NIR) fluorescence imaging using exogenous fluorescent agents provides whole-field images in real-time to assist the surgeon in the excision of a tumor. Although the method has high sensitivity, the specificity can sometimes be lower than expected. Raman spectroscopy can detect tumors with high specificity. Therefore, a combination of both techniques can be advantageous. A complication that must be addressed is that the NIR spectral region is favored by both techniques for (in vivo) tissue analysis. When fluorescence and Raman emissions spectrally overlap, it becomes challenging or impossible to detect the Raman signal. In this paper, by avoiding this overlap, we describe a Raman spectroscopy setup capable of recording high-quality Raman spectra from tissue containing NIR exogenous fluorescent agents. We identify an optimal wavelength interval (900-915 nm) for Raman excitation, which avoids both excitation of fluorescent dyes and Raman signal self-absorption by the tissue. In this way, Raman spectroscopy can be combined with the currently most-used NIR fluorescent dyes. This combined novel setup could pave the way for clinical trials benefiting from both fluorescence imaging and Raman spectroscopy to avoid positive margins in cancer surgery.

Intra-operative fluorescent imaging of endometriosis could help to optimize surgical treatment. Potential biomarkers to use as target for endometriosis-binding fluorescent probes were identified using a new five-phase transcriptomics-based approach to broaden the search for biomarkers. Using publicly available datasets, a differentially expressed gene (DEG) analysis was performed for endometriosis versus surgically relevant surrounding tissue (peritoneum, bladder, sigmoid, rectum, transverse colon, small intestine, vagina, and fallopian tubes) for which data was available. The remaining relevant surrounding tissues were analyzed for low expression levels. DEGs with a predicted membranous or extracellular location and with low expression levels in surrounding tissue were identified as candidate targets. Modified Target Selection Criteria were used to rank candidate targets based on the highest potential for use in fluorescent imaging. 29 potential biomarkers were ranked, resulting in Folate receptor 1 as the most potential biomarker. This is a first step towards finding a fluorescent tracer for intra-operative visualization of endometriosis. Additionally, this approach, using transcriptomics analysis to identifying candidate targets for a specific type of tissue for use in fluorescence-guided surgery could be translated to other surgical fields. Tweetable abstract: A new approach using transcriptomics analysis is shown to identify candidate targets for intra-operative fluorescent imaging for endometriosis, resulting in 29 potential candidates.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy in need of effective (immuno)therapeutic treatment strategies. For the optimal application and development of cancer immunotherapies, a comprehensive understanding of local and systemic immune profiles in patients with PDAC is required. Here, our goal was to decipher the interplay between local and systemic immune profiles in treatment-naïve patients with PDAC. METHODS: The immune composition of PDAC, matched non-malignant pancreatic tissue, regional lymph nodes, spleen, portal vein blood, and peripheral blood samples (collected before and after surgery) from 11 patients with PDAC was assessed by measuring 41 immune cell markers by single-cell mass cytometry. Furthermore, the activation potential of tumor-infiltrating lymphocytes as determined by their ability to produce cytokines was investigated by flow cytometry. In addition, the spatial localization of tumor-infiltrating innate lymphocytes in the tumor microenvironment was confirmed by multispectral immunofluorescence. RESULTS: We found that CD103+CD8+ T cells with cytotoxic potential are infrequent in the PDAC immune microenvironment and lack the expression of activation markers and checkpoint blockade molecule programmed cell death protein-1 (PD-1). In contrast, PDAC tissues showed a remarkable increased relative frequency of B cells and regulatory T cells as compared with non-malignant pancreatic tissues. Besides, a previously unappreciated innate lymphocyte cell (ILC) population (CD127-CD103+CD39+CD45RO+ ILC1-like) was discovered in PDAC tissues. Strikingly, the increased relative frequency of B cells and regulatory T cells in pancreatic cancer samples was reflected in matched portal vein blood samples but not in peripheral blood, suggesting a regional enrichment of immune cells that infiltrate the PDAC microenvironment. After surgery, decreased frequencies of myeloid dendritic cells were found in peripheral blood. CONCLUSIONS: Our work demonstrates an immunosuppressive landscape in PDAC tissues, generally deprived of cytotoxic T cells and enriched in regulatory T cells and B cells. The antitumor potential of ILC1-like cells in PDAC may be exploited in a therapeutic setting. Importantly, immune profiles detected in blood isolated from the portal vein reflected the immune cell composition of the PDAC microenvironment, suggesting that this anatomical location could be a source of tumor-associated immune cell subsets.