3069 Background: CD8 T cells mediate antitumor effects of immune checkpoint blockade (ICB); their histologically-determined abundance prior to or during therapy (Rx) appears to correlate with ICB response in melanoma (MEL) and other solid tumors. We performed this Phase IIb study to assess CD8 targeted PET imaging with 89 Zr-crefmirlimab berdoxam prior to and during ICB Rx to study its potential as a marker for Rx selection, enhancement or even replacement of existing tumor measurement systems, and correlation of clinical outcomes. Methods: 70 patients (pts) with MEL or Merkel cell cancer (MCC) (27), renal cell cancer (RCC) (35) or lung cancer (NSCLC) (8) who were eligible for first or second-line single- or double-agent ICB or ICB plus an oral kinase inhibitor (TKI) were enrolled. 89 Zr-crefmirlimab berdoxam (1 mCi,1.5 mg protein), was administered intravenously ≤2 weeks prior to cycle 1 of ICB Rx, followed by a PET/CT scan 24 (+/-3) hours later (baseline, BL). The 2nd tracer injection and associated PET/CT scan occurred 4-6 weeks after ICB Rx initiation, prior to cycle 3 (on treatment, OT). Standard of Care imaging and RECIST 1.1 were used to assess response to Rx. Results: All 70 pts were evaluable for safety analysis; none experienced an SAE related to imaging agent. 65 pts (21 MEL, 2 MCC, 34 RCC and 8 NSCLC) were included in the primary endpoint analysis of correlating CD8 PET scans with best confirmed overall response (BOR) by RECIST 1.1. MEL and MCC pts received single (6/23) or double ICB (17/23), RCC pts received single ICB with/without TKI (21/34) or dual ICB (13/34), and all NSLCL pts received single ICB. In the RCC cohort, multiple CD8 PET metrics showed statistically significant association with either individual BOR or Binary Response at BL, OT or as delta, including: Tumor Standard Uptake Value (SUV), Lymph Node (LN) SUV, relative percentage of CD8 negative or positive lesions and normal organ SUV. Normalization to reference organs improved the correlation with BOR for the combined cohorts and for the MEL/MCC cohort. Depending on clinical objectives, different classification rules to predict BOR were applied, prioritizing specificity for non-responders and sensitivity for responders (Table). These results were cohort-dependent, as each cohort exhibited a distinct distribution of SUVs. Conclusions: PET imaging can quantitate CD8 T cells with sufficient specificity and sensitivity to support further study in selection of pts for Rx regimens and assessing early response to therapy. Clinical trial information: NCT05013099 . Prediction of BOR by CD8 PET. Cohort Response Parameter Timepoint AUC 95% CI Sensitivity Specificity MEL + MCC CR+PR vs SD+PD Spleen SUVmean BL 0.67 0.44,0.90 87.5 60.0 MEL + MCC CR+PR vs SD+PD Tumor SUVmax normal. to thyroid Delta 0.70 0.46, 0.95 85.7 64.3 RCC CR+PR vs SD+PD Hottest LN SUVmax OT 0.84 0.65, 1.00 71.4 90.9 RCC CR vs PR+SD+PD % CD8 negative lesions Delta 0.96 0.87, 1.00 100.0 92.3

Abstract Systemic autoimmune connective tissue diseases (CTDs) are characterized by anti-nuclear antibodies, shared HLA-associated genetic risk, and frequent disease overlap, suggesting a central role for CD4+ T cells in pathogenesis. However, defining disease-driving CD4+ T-cell responses remains challenging due to their localization within lymphoid and affected tissues and the lack of approaches linking these responses to circulating counterparts. We combined [18F]-labeled thymidine PET/CT-guided tissue sampling, ex vivo antigen stimulation, and single-cell multiomics to characterize CD4+ T-cell responses in blood, PET-avid locoregional lymph nodes (LNs), and disease-affected tissues from patients with the immunologically distinct CTDs systemic sclerosis and Sjögren’s disease. PET-avid LNs from both diseases exhibited enhanced adaptive immune activity and contained an expanded population of interferon-stimulated gene (ISG)-expressing TRAIL+ CD4+ T cells. In Sjögren’s disease, active LNs and affected tissues harbored diverse effector CD4+ T-cell populations, including follicular and peripheral helper T cells and Th2/Th17 cells. In contrast, systemic sclerosis tissues lacked effector CD4+ T cells, while active LNs were enriched for naïve, regulatory, and TRAIL+ ISG CD4+ T cells. Antigen stimulation of peripheral blood mononuclear cells enriched for expanded effector CD4+ T-cell populations that shared activation profiles and clonal relationships with cells in LNs and affected tissues, many representing autoreactive antigen-specific T cells. TRAIL+ CD4+ T cells suppressed effector T-cell differentiation, autoreactive plasma cell generation, and autoantibody production in vitro, identifying a previously unrecognized immunoregulatory population. Together, this workflow enables comprehensive characterization of pathogenic and regulatory CD4+ T-cell responses across CTDs.

In vivo tracking T-lymphocytes is dramatically advancing our understanding of the complex immune landscape in a wide spectrum of autoimmune and cancer diseases. By providing new insights into intricate mechanisms, pathways, molecular interactions and dynamic nature of immune system, this approach paves the way for personalized therapies, tailored to individual patient need. Imaging T-cells is, indeed, emerging as a crucial tool not only for early disease detection, but also for personalized immune-therapy and treatment monitoring, thus enabling a “precision medicine”. T-lymphocytes offers several accessible molecular targets suitable for immune-imaging, including the well-characterized CD3, CD8 and CD4 surface markers. Consequently, significant efforts have been, and currently are, devoted to develop highly sensitive and specific radiopharmaceuticals for single photon emission tomography (SPECT), positron emission tomography (PET). These advanced tools aim to non-invasively visualize and quantify these key targets and to assess the functional status of T-lymphocytes within tumor microenvironment or sites of autoimmune inflammation. This narrative review aims at providing a deep overview of the main strategies adopted so far for imaging T-cells and their subsets, emphasizing current and prospective clinical applications in autoimmune diseases and immune-oncology. Furthermore, advancements and challenges in successfully translating these approaches into clinical practice will be also discussed. We will discuss the great potential of T-cells imaging to significantly improve patient’s outcome and revolutionize the management of these challangind diseases.

Score chart with predicted probability (%) to remain on WW at 12 months This model was based on the number of IMDC Risk factors (0, 1, 2), the number or involved organ sites (0 - 4) and the geometric mean [¹⁸F]FDG SUVmax as a continuous variable. The underlying formula is 100*(exp(-0.531)^exp(0.198*[IMDC score] + 0.039*[No of affected organ sites] + 0.170*[geometric mean [¹⁸F]FDG SUVmax] - 1.09))

CD4 + T cells are crucial in shaping response and resistance to immunotherapy. To enhance our understanding of their multifaceted functions, we developed copper-64–radiolabeled nanobodies targeting the human CD4 receptor ( 64 Cu-CD4-Nb1) for positron emission tomography (PET). In human CD4-receptor knock-in mice, 64 Cu-CD4-Nb1 specifically accumulated in different orthotopic tumors, correlating with histological CD4 + cell densities. Based on intratumoral CD4 + cell distribution patterns within the core and periphery, we distinguished responders to combined αPD-1/4-1BB antibodies early on-treatment. CD4-PET identified resistance to αPD-1 monotherapy, which was mitigated by adding regulatory T cell–depleting α4-1BB antibodies. Patients with early-stage non–small cell lung cancer who relapsed after neoadjuvant αPD-L1 therapy revealed low CD4 + T cell densities in the tumor core. In human and mouse tumor tissues, regulatory T cells correlated with CD4 + cell densities. Thus, visualizing the spatial distribution patterns of CD4 + cells by PET offers mechanistic insights into CD4-mediated therapy efficacy, with great potential for guiding combinatorial immunotherapies in patients with cancer.

Flow-chart patients according to RECIST-defined PD. *All patients had clinical disease progression; no CT-imaging was performed before initiation of systemic treatment ** In total 7 patients choose best supportive care. Three other patients underwent radiotherapy or surgery of all target lesions.

Background/Objectives: The prevalence of lung cancer in patients with a peripheral pulmonary nodule referred for navigation bronchoscopy (NB) is high. Combining NB with a systematic EBUS for staging is common practice. We investigated the added value of performing EBUS in the population referred for NB in relation to the available pre-procedural [18F]FDG-PET and CT imaging information. Methods: This single-center study evaluated all consecutive patients who underwent an NB in an academic referral center. [18F]FDG-PET and CT scoring of lymphadenopathy was based on routine [18F]FDG-PET and/or contrast-enhanced chest (ce) CT imaging reports and were correlated to outcome of systematic EBUS and subsequent surgery (when available). Results: In total, 403 patients were included for analysis of which 327 underwent EBUS (81.1%). In 138/403 patients (35%) who had positive lymph nodes on [18F]FDG-PET (86.5%) or ceCT (13.5%), 12 lung cancer patients were diagnosed with N+ disease by EBUS (8.4%). An additional nine EBUS-negative patients were diagnosed with N+ disease after surgery (5.4%). In the group of patients with imaging-negative lymph nodes (65.8%), no metastatic lymph nodes were found by EBUS, and surgery revealed occult nodal metastasis in eight patients (3.1%). Conclusions: In patients with peripheral pulmonary nodules referred for NB, EBUS may be safely omitted when [18F]FDG-PET or ceCT imaging does not indicate presence of nodal involvement.

Background:Achieving preoperative pathological confirmation and accurate clinical staging are crucial for neoadjuvant treatment decisions in resectable non-small cell lung cancer (NSCLC), though often challenging. This study examines the prevalence of missing preoperative pathological confirmation with focus on patients with clinical stage II or III NSCLC. In addition, pre- and postoperative staging discrepancies are studied in the presence of preoperative NSCLC confirmation. These two impeding factors were studied in an era before the introduction of neoadjuvant chemoimmunotherapy in resectable NSCLC. Methods:In this retrospective observational study, patients with resectable NSCLC diagnosed between 2015 and 2019 were selected. The prevalence of absent preoperative confirmation of NSCLC was evaluated. Stage migration was analyzed in the overall population and across two patient cohorts with either a present or absent upfront pathological NSCLC diagnosis. Relevant stage migration was assessed in the cohort with preoperative NSCLC confirmation. Relevant upstaging was defined as migration from clinical stage I to pathological stage IIA-IIIB and relevant downstaging from clinical stage IIA-IIIB to pathological stage I. Results:In 277 of 809 patients (34.2%), no preoperative pathological NSCLC diagnosis was obtained, including 83 patients with clinical stage II or III disease (30.0% and 10.3% of the total cohort). In 532 of 809 patients (65.8%), preoperative pathological NSCLC confirmation was achieved. In this cohort, relevant stage migration was noticed in 105 patients (19.7% and 13.0% of the total cohort). Conclusions:In the era before the introduction of neoadjuvant chemoimmunotherapy as standard of care, absent preoperative NSCLC confirmation or inaccurate staging occurred in nearly a quarter of potential candidates for neoadjuvant treatment. These two limiting factors will need to be addressed in order to adequately administer neoadjuvant therapy in patients with resectable NSCLC conform current guidelines.

Immune checkpoint inhibitors (ICI) boost the endogenous anticancer immunity, evoking long-lasting anticancer responses in a subset of patients with solid tumors. Simultaneously, ICI are also associated with serious toxicities, impacting treatment duration and the quality of life. The proposed processes underlying ICI-related toxicity include T-cell activation and recruitment to non-tumor tissues, involvement of other immune cells and fibroblasts and the host’ microbiome composition. However, the exact mechanisms of these processes remain incompletely understood, hindering clinicians’ ability to predict and identify ICI-related toxicity in the early stages of treatment. Molecular imaging may play a role as a non-invasive biomarker, providing a tool to study ICI-related toxicity. This review discusses the applications of molecular imaging to answer questions regarding the mechanisms, detection, and prediction of ICI-related toxicity. Potential targets and the current state of development of suitable imaging techniques are discussed.

Objective: We evaluated the feasibility of a machine-learning (ML) model based on clinical features and radiomics from [18F]FDG PET/CT images to differentiate between infected and non-infected intracavitary vascular grafts and endografts (iVGEI). Methods: Three ML models were developed: one based on pre-treatment criteria to diagnose a vascular graft infection (“MAGIC-light features”), another using radiomics features from diagnostic [18F]FDG-PET scans, and a third combining both datasets. The training set included 92 patients (72 iVGEI-positive, 20 iVGEI-negative), and the external test set included 20 iVGEI-positive and 12 iVGEI-negative patients. The abdominal aorta and iliac arteries in the PET/CT scans were automatically segmented using SEQUOIA and TotalSegmentator and manually adjusted, extracting 96 radiomics features. The best-performing models for the MAGIC-light features and PET-radiomics features were selected from 343 unique models. Most relevant features were combined to test three final models using ROC analysis, accuracy, sensitivity, and specificity. Results: The combined model achieved the highest AUC in the test set (mean ± SD: 0.91 ± 0.02) compared with the MAGIC-light-only model (0.85 ± 0.06) and the PET-radiomics model (0.73 ± 0.03). The combined model also achieved a higher accuracy (0.91 vs. 0.82) than the diagnosis based on all the MAGIC criteria and a comparable sensitivity and specificity (0.70 and 1.00 vs. 0.76 and 0.92, respectively) while providing diagnostic information at the initial presentation. The AUC for the combined model was significantly higher than the PET-radiomics model (p = 0.02 in the bootstrap test), while other comparisons were not statistically significant. Conclusions: This study demonstrated the potential of ML models in supporting diagnostic decision making for iVGEI. A combined model using pre-treatment clinical features and PET-radiomics features showed high diagnostic performance and specificity, potentially reducing overtreatment and enhancing patient outcomes.

Flow diagram of patient enrolment. * Four patients were unfit for systemic treatment due to clinical deterioration resulting from rapid disease progression (n=3) or comorbidity and age (n=1). Three other patients did not wat systemic treatment.

Introduction:Many immunotherapies focus on (re)invigorating CD8+ T cell anti-cancer responses. Different nuclear imaging techniques have been developed to measure CD8+ T cell distributions. Comprehensive comparisons of in vivo and ex vivo T cell labeling methods with respect to tumor and normal tissue targeting and correlation with CD8⁺ T cell presence are lacking, but essential for accurate clinical interpretation. We performed a head-to-head comparison of three CD8+ T cell imaging approaches: 89Zr-labeled Fc-silent anti-CD8 antibody ([89Zr]Zr-anti-CD8-IgG2asilent), ex vivo 89Zr-labeled ovalbumin-specific CD8+ T cells ([89Zr]Zr-OT-I), and 18F-labeled IL2 ([18F]AlF-RESCA-IL2). Methods:B16F10/OVA tumor-bearing C57BL/6 mice (n = 10/group) underwent PET/CT imaging at 72 ([89Zr]Zr-anti-CD8-IgG2asilent), 24 and 48 h ([89Zr]Zr-OT-I), and 10 min ([18F]AlF-RESCA-IL2) pi. Subsequently, biodistribution analysis was performed, followed by flow cytometry to evaluate intratumoral CD8+ T cell numbers. Intratumoral radiolabel distributions were assessed by autoradiography and immunohistochemistry. Results:All approaches showed uptake in CD8-rich tissues, with preferential spleen targeting. Biodistribution analyses showed tumor uptake exceeded blood level for [89Zr]Zr-anti-CD8-IgG2asilent and [89Zr]Zr-OT-I. Furthermore, their tumor uptake correlated to intratumoral CD8+ T cells presence even though intratumoral distribution patterns differed significantly. Conclusion:[89Zr]Zr-anti-CD8-IgG2asilent and [89Zr]Zr-OT-I PET/CT imaging can evaluate intratumoral CD8+ T cell infiltration. [89Zr]Zr-anti-CD8-IgG2asilent might be suited for TME immunophenotyping, while ex vivo labeling visualizes tumor migration and invasion dynamics of tumor-specific T cells. [18F]AlF-RESCA-IL2 uptake did not correlate to the intratumoral CD8+ T cell presence. Here, we provide new insights to guide the selection of imaging strategies for assessing relevant immunotherapy-specific aspects of the TME and support the correct interpretation of clinical CD8 imaging.

BACKGROUND:Selection of suitable candidates for intraoperative tumour detection and cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is important for improving outcomes for patients with colorectal peritoneal metastases. Previous research demonstrated the use of single-photon emission computed tomography (SPECT), intraoperative radiodetection, and near-infrared fluorescence (NIRF)-guided surgery with a dual-labelled 111In-labelled dodecane tetra-acetic acid (DOTA)-labetuzumab-IRDye800CW tracer to detect peritoneal metastases before operation. The aim of this study was to validate these results. METHODS:A single-centre phase II study was conducted to evaluate the safety and feasibility of 111In-labelled DOTA-labetuzumab-IRDye800CW in patients with colorectal peritoneal metastases undergoing CRS-HIPEC. SPECT/computed tomography (CT) was undertaken before surgery, after intravenous administration of 10 mg 111In-labelled DOTA-labetuzumab-IRDye800CW (mean 101.25 MBq). During surgery, radiodetection and NIRF imaging were used for tumour detection. Adverse events were assessed, and tumour-to-background ratios (TBRs) and peritoneal cancer index scores were analysed. RESULTS:Seven patients were included. No study-related severe adverse events were reported. Imaging before surgery revealed previously undetected metastases in one patient. The mean(standard deviation, s.d.) SPECT/CT peritoneal cancer index score was 3(2), and the intraoperative score was 14(7) (P = 0.032). A total of 52 lesions were removed during CRS, of which 37 were malignant. With NIRF imaging, 34 (92%) of 37 malignant lesions were detectable. Of 52 fluorescent lesions, 4 were false-positive. Mean(s.d.) fluorescence TBR was 3.4(1.8) and mean radiodetection TBR was 4.4(1.4). CONCLUSION:This study confirmed the safety and feasibility of multimodal image-guided surgery in patients with peritoneal metastases.

INTRODUCTION:Patients with stage III non-small cell lung cancer (NSCLC) are at high risk of developing post-treatment recurrences (50-78%) during follow-up. As more effective treatments are now available, especially for patients with oligometastatic disease, earlier detection of recurrences may prolong survival and health-related quality of life (HRQOL). With the use of 2'-deoxy-2'-[18F]fluoroglucose positron emission tomography/CT ([18F]FDG PET/CT) during follow-up, recurrences may be detected earlier. Therefore, the primary objective of this study is to compare the 3-year overall survival of patients with stage III NSCLC during follow-up surveillance with [18F]FDG PET/CT versus follow-up with conventional CT (usual care). Secondary objectives address the number, location and timing of recurrences, as well as HRQOL, cost-effectiveness and patient experiences of PET/CT scans. METHODS AND ANALYSIS:In this multicentre randomised controlled clinical trial, 690 patients with stage III NSCLC (8th edition International Association for the Study of Lung Cancer (IASLC) Tumor, Nodes, Metastasis (TNM) classification) who completed curative intended treatment and started follow-up care (which may include adjuvant therapy) will be randomised 1:1 to either the intervention ([18F]FDG PET/CT) or the control group (CT). Patients will undergo follow-up scans during visits at 6, 12, 18, 24 and 36 months. Data will be collected using validated questionnaires, electronic case report forms and data extractions from the electronic health records. Additionally, blood samples will be collected, and interviews will be conducted. ETHICS AND DISSEMINATION:The study protocol has been approved by the Medical Ethical Committee of the Radboudumc and review boards of all participating centres. Written informed consent will be obtained from all participants. Study results will be published in international peer-reviewed scientific journals and presented at relevant scientific conferences. Data will be published in a data repository or other online data archive. TRIAL REGISTRATION NUMBER:NCT06082492.

The advent of positron emission tomography (PET) combined with computed tomography (CT) in the field of inflammatory/infectious diseases heralds an era of personalised disease management using these noninvasive technologies. This nuclear medicine technique can be a useful tool in tuberculosis (TB) for assessing the extent of extrapulmonary disease, evaluating treatment response and identifying patients at higher risk of disease relapse. The fusion of functional imaging provided by PET with the anatomical and morphological details captured by CT has enabled clinicians to better understand the dynamics of the pathophysiology and natural course of Mycobacterium tuberculosis infection. Using its whole-body field of view, host responses are most commonly visualised using 18F-fluorodeoxyglucose, which reflects the glycolytic activity of cells. The strict indications for PET/CT in TB are matched by the caution required in interpreting its qualitative, quantitative and volumetric imaging patterns. In this narrative review, we aim to summarise evidence supporting the use of this molecular imaging modality in thoracic presentations of TB, particularly pulmonary and lymph node involvement, together with concepts to aid in the reporting and interpretation of the tests. We will also explore future indications for PET/CT in TB and discuss challenges to its routine use.

The upper respiratory tract (URT) is the entry site for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), from where it further disseminates. Early and effective adaptive immune responses are crucial to restrict viral replication and limit symptom development and transmission. Current vaccines increasingly incorporate strategies to boost mucosal immunity in the respiratory tract. Positron emission tomography (PET) is a non-invasive technology that measures cellular responses at a whole-body level. In this case series, we explored the feasibility of [89Zr]Zr-crefmirlimab berdoxam PET to assess CD8+ T-cell localization during active COVID-19. Our results suggest that CD8+ T-cell distributions assessed by PET imaging reflect their differentiation and functional state in blood. Therefore, PET imaging may represent a novel tool to visualize and quantify cellular immune responses during infections at a whole-body level.

Radiomics features can reveal hidden patterns in a tumor but usually lack an underlying biologic rationale. In this work, we aimed to investigate whether there is a correlation between radiomics features extracted from [18F]FDG PET images and histologic expression patterns of a glycolytic marker, monocarboxylate transporter-4 (MCT4), in pancreatic cancer. Methods: A cohort of pancreatic ductal adenocarcinoma patients (n = 29) for whom both tumor cross sections and [18F]FDG PET/CT scans were available was used to develop an [18F]FDG PET radiomics signature. By using immunohistochemistry for MCT4, we computed density maps of MCT4 expression and extracted pathomics features. Cluster analysis identified 2 subgroups with distinct MCT4 expression patterns. From corresponding [18F]FDG PET scans, radiomics features that associate with the predefined MCT4 subgroups were identified. Results: Complex heat map visualization showed that the MCT4-high/heterogeneous subgroup was correlating with a higher MCT4 expression level and local variation. This pattern linked to a specific [18F]FDG PET signature, characterized by a higher SUVmean and SUVmax and second-order radiomics features, correlating with local variation. This MCT4-based [18F]FDG PET signature of 7 radiomics features demonstrated prognostic value in an independent cohort of pancreatic cancer patients (n = 71) and identified patients with worse survival. Conclusion: Our cross-modal pipeline allows the development of PET scan signatures based on immunohistochemical analysis of markers of a particular biologic feature, here demonstrated on pancreatic cancer using intratumoral MCT4 expression levels to select [18F]FDG PET radiomics features. This study demonstrated the potential of radiomics scores to noninvasively capture intratumoral marker heterogeneity and identify a subset of pancreatic ductal adenocarcinoma patients with a poor prognosis.