Molecular Imaging and Biology

Imaging Cell Surface Plectin in PDAC Patients – A First-In-Human Phase 0 Study Report

Abstract Purpose Plectin is traditionally an intracellular cytoskeletal protein that maintains cell structure and stability. However, we and others have identified its surface-localized form in cancer (CSP), where it influences cell adhesion, migration, immune response, and tumor signaling. CSP-positive tumors (pancreatic, lung, ovarian, and breast cancers) contribute to over 3 million annual deaths, highlighting its clinical relevance. This phase 0 study aimed to evaluate PTP-01’s ability to target CSP in pancreatic tumors, despite their dense desmoplastic stroma, and to estimate CSP density and tumor vascularity. Methods Pancreatic cancer patients (n = 3) received an intravenous injection of 100 µg PTP-01 labeled with 370 MBq 111In one day before resection. Whole-body planar scintigraphy and SPECT imaging were performed at multiple time points. Resected tumors and adjacent tissues were collected 28 h post-injection. Blood and urine samples were obtained for pharmacokinetic analysis. Tissue biodistribution was assessed using whole-body SPECT scans. Results PTP-01 injection caused no reported adverse events. Uptake was primarily observed in the kidneys, liver, and bladder, with some tumor uptake. CSP density in tumors was estimated at 10⁶ molecules per cell. The elimination half-life (T₁/₂) ranged from 5 to 22 h across patients. Conclusion PTP-01 imaging of pancreatic tumors revealed the ability of a targeted agent to bind to CSP. Further, CSP density in tumors was estimated to be on par with other surface molecules such as Her2 with effective targeted therapies. This study suggests that CSP is a highly expressed, accessible molecule for the development of targeted therapies such as antibodies or antibody–drug conjugates.

Challenges in Pharmacokinetic Modelling of [18F]fluoro-PEG-folate PET/CT Imaging in Epithelial Ovarian Cancer Patients

Abstract Purpose To describe the pharmacokinetic properties of the [18F]fluoro-polyethylene glycol(PEG)-folate radiotracer in PET/CT imaging of patients with advanced stage epithelial ovarian cancer (EOC). Procedures In five patients with advanced EOC (FIGO stage IIIB/IIIC, Fédération Internationale de Gynécologie et d’Obstétrique), a 90-min dynamic PET acquisition of the pelvis was performed directly after i.v. administration of 185 MBq [18F]fluoro-PEG6-folate. Arterial blood samples collected at nineteen timepoints were used to determine the plasma input function. A static volume of interest (VOI) for included tumor lesions was drawn manually on the PET images. Modelling was performed using PMOD software. Three different models (a 1-tissue compartment model (1T2k) and two 2-tissue compartment models, irreversible (2T3k) and reversible (2T4k)) were compared in goodness of fit with the time activity curves by means of the Akaike information criterion. Results The pharmacokinetic analysis in the pelvic area has proven to be much more challenging than expected. Only four out of 22 tumor lesions in five patients were considered suitable to perform modelling on. The remaining tumor lesions were inapt due to either low tracer uptake, small size, proximity to other [18F]fluoro-PEG6-folate -avid structures and/or displacement by abdominal organ motion in the dynamic scan. Data from the four analyzed tumor lesions suggest that the irreversible 2T3k may best describe the pharmacokinetics. All 22 lesions were immunohistochemically stained positive for the folate receptor alpha (FRα) after resection. Conclusion Performing pharmacokinetic analysis in the abdominal pelvic region is very challenging. This brief article describes the challenges and pitfalls in pharmacokinetic analysis of a tracer with high physiological accumulation in the intestines, in case of lesions of limited size in the abdominal pelvic area.

PET/MRI and PET/CT Radiomics in Primary Cervical Cancer: A Pilot Study on the Correlation of Pelvic PET, MRI, and CT Derived Image Features

To evaluate the correlation of radiomic features in pelvic [2-deoxy-2-18F]fluoro-D-glucose positron emission tomography/magnetic resonance imaging and computed tomography ([ Nineteen patients with histologically confirmed primary squamous cell carcinoma of the cervix underwent same-day [ For a total of 101 extracted features, 1104/5050 pairs of features showed a significant correlation (ρ ≥ 0.70, p < 0.05). There was a strong correlation between 190/484 PET pairs of features from PET/MRI and PET/CT, 91/418 pairs of CT and PET from PET/CT, 79/418 pairs of T2 and PET from PET/MRI, and 50/418 pairs of ADC and PET from PET/MRI. Significant difference was seen between eight features in local and metastatic tumors including MTV, TLG, and entropy on PET from PET/CT; MTV and TLG on PET from PET/MRI; compactness and entropy on T2; and entropy on ADC images. We demonstrated strong correlation of many extracted radiomic features between PET/MRI and PET/CT. Eight radiomic features calculated on PET/CT and PET/MRI were significantly different between local and metastatic CCa. This study paves the way for future studies to evaluate the diagnostic and predictive potential of radiomics that could guide clinicians toward personalized patients care.

Non-invasive Differentiation of Endometrial Adenocarcinoma from Benign Lesions in the Uterus by Utilization of Amide Proton Transfer-Weighted MRI

To evaluate the utility of three-dimensional (3D) amide proton transfer-weighted (APTw) imaging for differentiation of endometrial adenocarcinoma and uterine benign lesions. This prospective study enrolled 22 normal volunteers and 113 patients with suspicious uterine lesions, including endometrial adenocarcinoma, leiomyoma, and adenomyosis. Pelvic APTw MRI was performed on a 3-T MRI scanner with default APTw parameters. Two radiologists blindly evaluated uterine lesion APTw image quality by a 3-point Likert scale and independently measured APTw values on images with excellent to good image quality. Inter-reader agreement was evaluated. The Mann-Whitney U test with Bonferroni correction was used to compare the differences among different types of uterine lesions. A receiver operating characteristic analysis was performed. A total of 111 lesions (33 endometrial adenocarcinoma, 26 leiomyoma, and 52 adenomyosis lesions) from 99 patients revealing a majority of good quality with excellent inter-reader agreement were included for the image quality evaluation. APTw values of endometrial adenocarcinoma were 2.9 ± 0.1 %, significantly higher than those of leiomyoma (1.9 ± 0.1 %), adenomyosis (2.2 ± 0.1 %), and normal uterine myometrium (1.9 ± 0.1 %) (all p < 0.0001). The area under the receiver operating characteristic curve for differentiating endometrial adenocarcinoma from leiomyoma, adenomyosis, and myometrium was 0.87, 0.85, and 0.91, respectively. Feasible threshold APTw values of each group were determined as 2.4 %, 2.7 %, and 2.4 % with a sensitivity of 83.3 %, 76.7 %, and 83.3 % and a specificity of 83.3 %, 81.6 %, and 86.4 %, respectively. Malignant endometrial adenocarcinoma had significantly higher APTw values than leiomyoma, adenomyosis, and normal uterine myometrium. Our study adds to the growing body of validation on 3D APTw imaging and uterine lesions.

Evaluation of Pafolacianine (Cytalux®) for Fluorescence-Guided Surgery in Head and Neck Squamous Cell Carcinoma: A Negative Study with Important Clinical Implications

Abstract Background Pafolacianine (Cytalux ® ) represents the first FDA-approved tumor-specific fluorescence imaging agent, demonstrating efficacy in ovarian cancer through folate receptor-α (FR-α) targeting. Given the need for improved intraoperative margin assessment in head and neck squamous cell carcinoma (HNSCC), where positive surgical margins occur in 10–30% of cases, we investigated the potential utility of pafolacianine for fluorescence-guided surgery in HNSCC models. Objective To evaluate the feasibility of visualizing HNSCC using pafolacianine in vitro , in vivo , and clinical tissue analysis, with comparison to fluorescence-guided surgery agents that have been successful in patients. Methods HNSCC cell lines (FaDu, UMSCC47) were treated with escalating concentrations of pafolacianine (0–500 nM) and assessed for binding at 1 and 24 h. Nude mice bearing HNSCC xenografts (FaDu, UMSCC47) received intraperitoneal injection of pafolacianine (10 nmol) with fluorescence imaging at multiple timepoints. Immunohistochemistry analysis of patient samples ( n  = 8 tumor, n  = 8 normal) evaluated FR-α and FR-β expression. Panitumumab-IRDye800CW served as a positive control for comparison. Results In vitro analysis demonstrated minimal pafolacianine binding across all HNSCC cell lines, with fluorescence intensities similar to or lower than the FR-α-negative A549 control cell line. In vivo imaging revealed poor tumor localization with mean fluorescence intensity (MFI) of 7.39 (FaDu) and 6.97 (UMSCC47), substantially lower than non-target tissues including skin. Immunohistochemistry analysis showed no statistically significant difference in FR-α expression between tumor and normal tissue (p &gt; 0.05). For comparison, panitumumab-IRDye800CW demonstrated robust tumor targeting with MFI of 32.14 (FaDu) and 14.98 (UMSCC47). Conclusions This study demonstrates that pafolacianine exhibits limited utility for fluorescence-guided surgery in HNSCC due to insufficient FR-α expression and poor tumor-to-background contrast. These negative findings provide crucial evidence against the clinical translation of pafolacianine for HNSCC applications and highlight the importance of target expression validation in precision medicine approaches. Clinical Relevance Negative studies such as this are essential for evidence-based clinical decision-making, preventing unnecessary resource allocation and potential patient exposure to ineffective interventions. These findings inform the broader fluorescence-guided surgery field and support continued investigation of alternative targeting strategies for HNSCC.

Comparison of Five Near-Infrared Fluorescent Folate Conjugates in an Ovarian Cancer Model

Abstract Purpose Fluorescence imaging (FLI) using targeted near-infrared (NIR) conjugates aids the detection of tumour lesions pre- and intraoperatively. The optimisation of tumour visualisation and contrast is essential and can be achieved through high tumour-specificity and low background signal. However, the choice of fluorophore is recognised to alter biodistribution and clearance of conjugates and is therefore a determining factor in the specificity of target binding. Although ZW800-1, IRDye® 800CW and ICG are the most commonly employed NIR fluorophores in clinical settings, the fluorophore with optimal in vivo characteristics has yet to be determined. Therefore, we aimed to characterise the impact the choice of fluorophore has on the biodistribution, specificity and contrast, by comparing five different NIR fluorophores conjugated to folate, in an ovarian cancer model. Procedures ZW800-1, ZW800-1 Forte, IRDye® 800CW, ICG-OSu and an in-house synthesised Cy7 derivative were conjugated to folate through an ethylenediamine linker resulting in conjugates 1–5, respectively. The optical properties of all conjugates were determined by spectroscopy, the specificity was assessed in vitro by flow cytometry and FLI, and the biodistribution was studied in vivo and ex vivo in a subcutaneous Skov-3 ovarian cancer model. Results We demonstrated time- and receptor-dependent binding of folate conjugates in vitro and in vivo. Healthy tissue clearance characteristics and tumour-specific signal varied between conjugates 1–5. ZW800-1 Forte (2) revealed the highest contrast in folate receptor alpha (FRα)-positive xenografts and showed statistically significant target specificity. While conjugates 1, 2 and 3 are renally cleared, hepatobiliary excretion and no or very low accumulation in tumours was observed for 4 and 5. Conclusions The choice of fluorophore has a significant impact on the biodistribution and tumour contrast. ZW800-1 Forte (2) exhibited the best properties of those tested, with significant specific fluorescence signal.

Application of a Machine Learning Approach for the Analysis of Clinical and Radiomic Features of Pretreatment [18F]-FDG PET/CT to Predict Prognosis of Patients with Endometrial Cancer

To examine the prognostic significance of pretreatment 2-deoxy-2-[ Included in this retrospective study were 53 patients with endometrial cancers who underwent [ The five best predictors of disease progression were coarseness, gray-level run length nonuniformity, stage, treatment method, and gray-level zone length nonuniformity. The kNN model obtained the best performance classifier for predicting the disease progression (AUC =0.890, accuracy =0.849, F1 score =0.848, precision =0.857, and recall =0.849). Coarseness which was the first ranked radiomic feature was selected for survival analyses, and only coarseness remained as a significant and independent factor for both PFS (hazard ratios (HR), 0.65; 95 % confidence interval [CI], 0.49-0.86; p=0.003) and OS (HR, 0.52; 95 % CI, 0.36-0.76; p<0.001) at multivariate Cox regression analysis. [