Whole body PD-1 and PD-L1 positron emission tomography in patients with non-small-cell lung cancer

Efficacy of radiolabelled PD-L1-targeted nanobody in predicting and evaluating the combined immunotherapy and chemotherapy for resectable non-small cell lung cancer

BACKGROUND

This study aimed to assess the predictive and evaluative value of PD-L1 targeted 68Ga-THP-APN09 PET/CT in the neoadjuvant immunotherapy combined with chemotherapy for resectable non-small cell lung cancer (NSCLC), and to explore its potential in indicating immunotherapy-related adverse effects (irAEs).

METHODS

Fifty patients with resectable NSCLC enrolled in this prospective study underwent baseline 68Ga-THP-APN09 PET/CT and 18F-FDG PET/CT, with follow-up 18F-FDG PET/CT conducted, additionally, 36 patients received follow-up 68Ga-THP-APN09 PET/CT. Surgery was performed following 2-4 cycles of toripalimab combined with chemotherapy if R0 resection was feasible. The major pathologic response (MPR) state of the post-operative specimen and the adverse effects following combined therapy were documented. The correlation between PD-L1 expression and baseline 68Ga-THP-APN09 PET/CT uptake was determined. The predictive and evaluative efficacies of baseline and follow-up 68Ga-THP-APN09 PET/CT, along with 18F-FDG PET/CT, in determining MPR, were compared.

RESULTS

The SUVmax values of baseline 68Ga-THP-APN09 PET/CT were significantly higher in patients exhibiting high-positive PD-L1 expression compared to those with low-positive and negative expression (P = 0.001). And the SUVmax values of baseline 68Ga-THP-APN09 PET/CT in the response group, as determined by 18F-FDG PET/CT evaluation, were significantly higher than those in the non-response group (3.4 vs. 2.4, P < 0.001). Totally, 41 patients underwent surgery, of which 27 achieved MPR, while 14 did not. The SUVmax in baseline 68Ga-THP-APN09 PET/CT demonstrated statistical significance between the MPR and non-MPR groups, with area under the ROC curve (AUC) of 0.88 (95%CI: 0.77-0.99) in identifying MPR. However, the SUVmax in baseline 18F-FDG PET/CT failed to demonstrated significant predictive power, with AUC values of 0.68 (95%CI: 0.50-0.86, P = 0.076). While the SUVmax in follow-up 68Ga-THP-APN09 and 18F-FDG PET/CT, along with their change rate (ΔSUVmax%), demonstrated good predictive efficacy in identifying MPR, with AUC values of 0.81 (0.64-0.98), 0.91 (0.82-1.00), 0.93 (0.84-1.00), and 0.96 (0.89-1.00), respectively. Furthermore, the follow-up 68Ga-THP-APN09 PET/CT could remarkedly indicate the potential for thyroiditis.

CONCLUSION

Baseline 68Ga-THP-APN09 PET/CT alone could predict efficacy and assist in patient screening for immunotherapy combined chemotherapy in resectable NSCLC, and the follow-up 68Ga-THP-APN09 PET/CT and their change rates could aid in therapy evaluation. Additionally, follow-up 68Ga-THP-APN09 PET/CT could be utilized to monitor the immunotherapy-related thyroiditis during the therapy.

TRIAL REGISTRATION

NCT05156515, registered 8 December 2021, https://register.

CLINICALTRIALS

gov/prs/app/action/SelectProtocol?sid=S000BMSI%26;selectaction=Edit%26;uid=U000503E%26;ts=2%26;cx=zeghuw .

PD-L1 imaging with [99mTc]NM-01 SPECT/CT is associated with metabolic response to pembrolizumab with/without chemotherapy in advanced lung cancer

BACKGROUND

Programmed death-ligand 1 (PD-L1) immunohistochemistry is a predictive biomarker for anti-PD-(L)1 therapy in non-small cell lung cancer (NSCLC). It is not a reliable predictor of clinical benefit with non-invasive imaging providing a potential solution. We present the PECan study, the aim of which to assess the relationship of [99mTc]-labeled anti-PD-L1 single-domain antibody (NM-01) single-photon emission computed tomography (SPECT)/CT with metabolic response to anti-PD-(L)1.

METHODS

PD-L1 tumour proportion score (TPS) measured using SP263 assay. [99mTc]NM-01 SPECT/CT and [18F]FDG PET/CT performed before and 9-weeks following pembrolizumab with/without chemotherapy in patients with advanced NSCLC. Tumor (T) to blood pool (BP) maximum region of interest (ROImax) measurements performed in primary and metastatic lesions using SPECT/CT images.

RESULTS

Fifteen patients were included (median age 63 years, 9 male). Intertumoural heterogeneity evident in 10(67%) patients. Mean [99mTc]NM-01 T:BP demonstrated moderate correlation with PD-L1 TPS (r = 0.45, p < 0.05). Depth of [18F]FDG PET/CT metabolic response at 9-weeks (n = 13), correlated strongly with baseline [99mTc]NM-01 T:BP (r = -0.73, p < 0.05), but only moderately with PD-L1 TPS (r = -0.46, p = 0.06).

CONCLUSION

[99mTc]NM-01 SPECT/CT allows non-invasive quantification of PD-L1 in primary tumour and metastases in NSCLC. [99mTc]NM-01 uptake moderately correlates with PD-L1 immunohistochemistry, determines heterogeneity, and is associated with early metabolic response to anti-PD-1 pembrolizumab.

CLINICAL TRIALS REGISTRATION

PD-L1 Expression in Cancer (PECan) study (NCT04436406), registered 18 June 2020 https://clinicaltrials.gov/ct2/show/NCT04436406.

Head-to-head comparison of peptide-based and nanobody-based radiotracers in detecting PD-L1 expression in non-small cell lung cancer

BACKGROUND

Immunotherapy based on programmed cell death protein receptor 1 and its ligand (PD-1/PD-L1) has become an important method for treating non-small cell lung cancer (NSCLC). Peptide-based and nanobody-based PET tracers offer potential advantages in PD-L1 detection, yet their comparative tumor uptake and biodistribution remain unclear. This study aimed to evaluate and compare [68Ga]Ga-DOTA-WL12 (a peptide-based tracer) and [68Ga]Ga-NOTA-RW102 (a nanobody-based tracer) in assessing PD-L1 expression in primary and metastatic NSCLC, providing insights for future radiotracer design and theranostic applications.

METHODS

Ten patients diagnosed with NSCLC underwent [68Ga]Ga-DOTA-WL12 and [68Ga]Ga-NOTA-RW102 PET/CT scans, with four of these patients also receiving [18F]FDG PET/CT scans. The tracer uptakes, quantified by maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), and target-to-background ratio (TBR), were compared between [68Ga]Ga-DOTA-WL12 and [68Ga]Ga-NOTA-RW102 PET/CT.

RESULTS

DOTA-WL12 and NOTA-RW102 exhibited favorable binding affinities with PD-L1, with equilibrium dissociation constant (KD) values of 0.2 nM and 0.0047 nM, respectively. Subsequent human studies revealed significant variations (P < 0.05) in the uptake of [68Ga]Ga-DOTA-WL12 and [68Ga]Ga-NOTA-RW102 across the liver (SUVmean: 20.43 ± 4.26 vs. 6.12 ± 1.36, p = 0.015), kidney (SUVmean: 2.40 ± 0.34 vs. 22.37 ± 2.88, P = 0.015), spleen (SUVmean: 2.44 ± 0.67 vs. 18.49 ± 3.90, P = 0.015), and lung background (SUVmean: 0.18 ± 0.12 vs. 1.09 ± 0.29, P = 0.015). Meanwhile, we found that the correlation between SUVmax and PD-L1 TPS was significantly stronger with [68Ga]Ga-DOTA-WL12 compared to [68Ga]Ga-NOTA-RW102 (P < 0.0001, r = 0.9471 vs. P = 0.0241, r = 0.5235).

CONCLUSION

The uptake of peptide-based [68Ga]Ga-DOTA-WL12 was more strongly correlated with PD-L1 TPS in primary and metastatic tumor lesions compared to [68Ga]Ga-NOTA-RW102. They also displayed different distribution, suggesting that peptide-based and nanobody-based radiotracers may have different clinical implications, particularly in radiotherapy.

Recent advances in biomarkers for predicting the efficacy of immunotherapy in non-small cell lung cancer

Lung cancer continues to be the primary cause of cancer-related deaths globally, with non-small cell lung cancer (NSCLC) accounting for approximately 85% of all instances. Recently, immune checkpoint inhibitors (ICIs) have transformed the treatment approach for NSCLC, however, only a subset of patients experiences significant benefits. Therefore, identifying reliable biomarkers to forecast the efficacy of ICIs is crucial for ensuring the safety and effectiveness of treatments, becoming a major focus of current research efforts. This review highlights the recent advances in predictive biomarkers for the efficacy of ICIs in the treatment of NSCLC, including PD-L1 expression, tertiary lymphoid structures (TLS), tumor-infiltrating lymphocytes (TILs), tumor genomic alterations, transcriptional signatures, circulating biomarkers, and the microbiome. Furthermore, it underscores the pivotal roles of liquid biopsy, sequencing technologies, and digital pathology in biomarker discovery. Special attention is given to the predictive value of TLS, circulating biomarkers, and transcriptional signatures. The review concludes that the integration of multiple biomarkers holds promise for achieving more accurate efficacy predictions and optimizing personalized immunotherapy strategies. By providing a comprehensive overview of the current progress, this review offers valuable insights into biomarker-based precision medicine for NSCLC and outlines future research directions.

Exploring molecular imaging to investigate immune checkpoint inhibitor-related toxicity

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.

Synthesis and preclinical evaluation of an Al18F radio-fluorinated bivalent PD-L1 nanobody

Immunotherapy targeting the programmed death 1/programmed death ligand 1 (PD-1/PD-L1) pathway has achieved remarkable clinical success, but there is a shortage of effective approaches for screening suitable patients. Recently developed PD-L1 nanobody probes have limitations, including limited availability of radionuclides, short tumor retention times, and accumulation in non-target organs. To enhance tumor retention and improve tumor-to-normal tissue contrast, we herein report the synthesis and preclinical evaluation of two Al18F-labeled bivalent PD-L1 nanobody probes ([18F]TzTCO-BINb109 and [18F]RESCA-BINb109). Preliminary results indicated that [18F]TzTCO-BINb109 had a greater affinity for PD-L1 and better stability than [18F]RESCA-BINb109. Micro-PET/CT revealed that [18F]TzTCO-BINb109 uptake in A549-PDL1 tumors peaked at 240 min post-injection (3.19 ± 0.49 %ID/g) and demonstrated sustained retention without in vivo defluorination. In contrast, [18F]RESCA-BINb109 exhibited shorter tumor retention (at 60 and 240 min, 2.08 ± 0.22 and 1.37 ± 0.26 %ID/g, respectively) and significant defluorination in vivo. Ex vivo biodistribution studies revealed that the tumor uptake of [18F]TzTCO-BINb109 was consistent with the PET results, with the highest uptake by A549-PDL1 tumor cells (3.43 ± 0.94 %ID/g) compared with H1975 (0.93 ± 0.18 %ID/g) and A549 (0.68 ± 0.12 %ID/g) cells observed at 240 min post-injection. Compared with the previously reported monomeric PD-L1-targeting nanobody probe, [68Ga]NOTA-Nb109, [18F]TzTCO-BINb109 demonstrated enhanced tumor uptake, prolonged retention, and superior tumor-to-normal tissue contrast, contributing to higher imaging quality. These results confirmed that the bivalent PD-L1 nanobody radioligand, [18F]TzTCO-BINb109, was a promising diagnostic probe for PD-L1 detection, efficacy evaluation, and prescription optimization of immune checkpoint inhibitor therapies.

TP53-centric ctDNA complements PET/CT for non-invasive assessment of pathological complete response and survival after neoadjuvant immunochemotherapy in esophageal squamous cell carcinoma: a prospective cohort study

BACKGROUND

Accurate assessment of pathologic complete response (pCR) after neoadjuvant immunochemotherapy (NICT) is crucial to implement active surveillance or tailor therapeutic strategies for esophageal squamous cell carcinoma (ESCC), while reliable non-invasive methods for pCR prediction are lacking. We aimed to evaluate the potential of integrating circulating tumor DNA (ctDNA) and PET/CT for predicting pCR to NICT for ESCC.

METHODS

A total of 123 eligible patients were enrolled, including 68 patients from our prospective clinical trial (ChiCTR2000028900) and a real-world study (NCT04822103) that formed the discovery cohort, as well as 55 patients from another clinical trial (ChiCTR2100051763) comprising the validation cohort. Blood samples for ctDNA sequencing and PET/CT metrics were collected before and after NICT.

RESULTS

The ctDNA status and PET/CT parameters at the post-NICT stage rather than the pre-NICT stage significantly differentiated pCR from non-pCR patients. ctDNA and PET/CT synergistically enhanced the prediction of pCR from perspectives of sensitivity and specificity, respectively. The model integrating ctDNA concentration and mean standardized uptake value (SUVmean) demonstrated area under curves (AUCs) of 0.860 in the discovery cohort and 0.798 in the validation cohort for pCR prediction and stratified patients into high- and low-risk groups with differential survival prospects. The key gene modules converged on TP53 as the core mutation for pCR prediction, among which those located in the exon regions contributed the most to its predictive capacity. The model constructed based on TP53 mutation and SUVmean differentiated pCR from non-pCR with comparable performance to the model based on PET/CT and the overall ctDNA concentration.

CONCLUSION

The combination of post-treatment TP53 -centric ctDNA and PET/CT synergistically enhances the prediction of pCR following NICT in ESCC patients, indicating the potential to inform clinical decision-making for these patients.

Artificial Intelligence for Drug Discovery: An Update and Future Prospects

Artificial intelligence (AI) has become a pivotal tool for medical image analysis, significantly enhancing drug discovery through improved diagnostics, staging, prognostication, and response assessment. At a high level, AI-driven image analysis enables the quantification and synthesis of previously qualitative imaging characteristics, facilitating the identification of novel disease-specific biomarkers, patient risk stratification, prognostication, and adverse event prediction. In addition, AI can assist in response assessment by capturing changes in imaging "phenotype" over time, allowing for optimized treatment plans based on real-time analysis. Integrating this emerging technology into drug discovery pipelines has the potential to accelerate the identification and development of new pharmaceuticals by assisting in target identification and patient selection, as well as reducing the incidence, and therefore cost, of failed trials through high-throughput, reproducible, and data-driven insights. Continued progress in AI applications will shape the future of medical imaging, ultimately fostering more efficient, accurate, and tailored drug discovery processes. Herein, we offer a comprehensive overview of how AI enhances medical imaging to inform drug development and therapeutic strategies.

Molecular probes for in vivo optical imaging of immune cells

Advancing the understanding of the various roles and components of the immune system requires sophisticated methods and technology for the detection of immune cells in their natural states. Recent advancements in the development of molecular probes for optical imaging have paved the way for non-invasive visualization and real-time monitoring of immune responses and functions. Here we discuss recent progress in the development of molecular probes for the selective imaging of specific immune cells. We emphasize the design principles of the probes and their comparative performance when using various optical modalities across disease contexts. We highlight molecular probes for imaging tumour-infiltrating immune cells, and their applications in drug screening and in the prediction of therapeutic outcomes of cancer immunotherapies. We also discuss the use of these probes in visualizing immune cells in atherosclerosis, lung inflammation, allograft rejection and other immune-related conditions, and the translational opportunities and challenges of using optical molecular probes for further understanding of the immune system and disease diagnosis and prognosis.

Radiolabelled anti-PD-L1 peptide PET/CT in predicting the efficacy of neoadjuvant immunotherapy combined with chemotherapy in resectable non-small cell lung cancer

BACKGROUND

This study aimed to evaluate the predictive value of baseline PD-L1 targeted peptide 68Ga-NOTA-WL12 PET/CT in neoadjuvant immunotherapy combined with chemotherapy of resectable NSCLC.

METHODS

Patients with resectable NSCLC (n = 20) enrolled in this prospective study received baseline paired 68Ga-NOTA-WL12 PET/CT and 18F-FDG PET/CT. After 2-4 cycles of toripalimab plus nab-paclitaxel and cisplatin, surgery was performed if R0 resection was available. The major pathologic response (MPR) state of the post-operative specimen was recorded. The imaging parameters of the 68Ga-NOTA-WL12 PET/CT, 18F-FDG PET/CT and CT between the MPR and non-MPR groups and their predictive efficacy of MPR were compared.

RESULTS

Among 20 patients, 17 patients underwent surgery, 10 achieved an MPR and 7 did not. The SUVmax and tumour-to-blood pool (TBR) of baseline 68Ga-NOTA-WL12 in the MPR group were higher than those in the non-MPR group, and the difference in TBR was statistically significant. The ΔSULpeak% of 18F-FDG exhibited differences between the MPR and non-MPR groups with no significance. Baseline 18F-FDG PET/CT parameters and ΔD% failed to differentiate the two groups. The areas under the ROC curves of SUVmax, TBR in 68Ga-NOTA-WL12 PET/CT, ΔD% and ΔSULpeak% in 18F-FDG PET/CT were 0.76, 0.79, 0.71 and 0.80, respectively, in predicting MPR.

CONCLUSION

Baseline 68Ga-NOTA-WL12 PET/CT has a potential to predict the pathological response of neoadjuvant immunotherapy combined with chemotherapy in patients with resectable NSCLC, whose efficacy is comparable to that of therapy evaluations employing baseline and follow-up CT and 18F-FDG PET/CT examinations.

TRIAL REGISTRATION

NCT04304066, registered 13 November 2020, https://register.

CLINICALTRIALS

gov/prs/app/action/SelectProtocol?sid=S000AEI9&selectaction=Edit&uid=U000503E&ts=2&cx=-awajet .

Evaluation of ImmunoPET in the efficacy and prognosis of immunotherapy for lung cancer

Advances in immune oncology have established immunotherapy as the first-line standard treatment for lung cancer; however, its efficacy remains limited to a subset of patients. Developing predictive biomarkers within the tumor microenvironment (TME) to assess the efficacy and prognosis of immunotherapy can enhance drug development and treatment strategies. Immuno-positron emission tomography (ImmunoPET) non-invasively visualizes the biological distribution of key targets in the TME using highly specific, radiolabeled tracers. PET imaging of the TME can serve as a reliable biomarker for predicting and monitoring responses to immune therapy, complementing existing immunohistochemical techniques. This review will focus on the development of ImmunoPET biomarkers, as well as the application of corresponding tracers and radionuclides in lung cancer. We will focus on available clinical tracers and those under development, outlining each TME target and its clinical validation for tumor immunotherapy efficacy and prognosis, while discussing the latest advances that may enhance ImmunoPET in future.

68Ga-Labeled Peptide for Noninvasive Quantifying Tumor Exposure of PD-L1 Therapeutics

PURPOSE

Targeting the programmed death protein 1/programmed death-ligand 1 (PD-1/PD-L1) immune checkpoint blockade therapy plays a critical role in cancer therapy. However, not all patients benefit from this approach, with PD-L1 expression levels being a significant contributing factor. Positron emission tomography (PET) imaging of PD-L1 offers a noninvasive, whole-body, and dynamic assessment of its expression. This study aims to develop a novel peptide-based PD-L1 tracer, [68Ga]HF12, to quantitatively evaluate PD-L1 expression in tumors, thereby offering clinical guidance.

METHODS

HF12 was successfully synthesized and radiolabeled with 68Ga to yield [68Ga]HF12. In vitro binding assays confirmed the specific binding affinity of HF12 for PD-L1 using CHO-hPD-L1 and CHO cell lines. Subsequent in vivo positron emission tomography (PET) imaging and biodistribution studies assessed [68Ga]HF12 for monitoring PD-L1 expression levels in tumor-bearing mice, including those subjected to immunotherapy. Furthermore, PD-L1 expression in tumor tissues was evaluated by using autoradiography, Western blotting, and immunohistochemical (IHC) analysis.

RESULTS

The synthesis of [68Ga]HF12 was successfully achieved with a radiochemical purity and yield exceeding 95%. Cellular uptake studies indicated that [68Ga]HF12 demonstrated both high specificity and significant uptake in PD-L1-positive CHO-hPD-L1 cells. Micro-PET imaging and biodistribution studies revealed that [68Ga]HF12 was preferentially accumulated in CHO-hPD-L1 tumors compared to PD-L1-negative CHO tumors. Treatment with Atezolizumab resulted in a significant reduction in [68Ga]HF12 uptake in CHO-hPD-L1 tumors relative to pretreatment levels, whereas no significant changes were observed in the phosphate-buffered saline (PBS) control group. Subsequent biodistribution studies, along with Western blotting and immunohistochemical analyses, confirmed that PD-L1 expression levels in tumors were reduced following immunotherapy, consistent with the results obtained from PET imaging.

CONCLUSIONS

[68Ga]HF12 was successfully synthesized as a radiotracer for noninvasive quantitative PET imaging of PD-L1 expression levels. This radiotracer exhibited the potential to quantify PD-L1 expression across various tumors, thereby facilitating the prediction of patient response to anti-PD-1 and anti-PD-L1 immunotherapies and monitoring therapeutic efficacy.

Preclinical and first‑in‑human evaluation of [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P PET imaging to assess tumor PD-L1 expression

PURPOSE

PD-L1 PET imaging can provide a non-invasively and real-time assessment of PD-L1 expression status at tumor sites. This study aimed to evaluate the targeting efficacy and biodistribution of a novel peptide-based PD-L1 PET agent, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P, in preclinical studies and human participants.

METHODS

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P was synthesized and the probe stability was analyzed in vitro and in vivo. Cellular uptake of the probe was evaluated using tumor cell lines with different PD-L1 expression levels. Small animal PET imaging and semi-quantitative studies were conducted in PC3, H1975 and A549 tumor-bearing mice models, with tumor PD-L1 expression confirmed through immunofluorescence and immunohistochemistry. Furthermore, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P PET imaging was performed in 1 healthy volunteer and 14 lung cancer patients to assess biodistribution and PD-L1 expression at tumor sites.

RESULTS

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P exhibited a radiochemical purity of > 99% and had good stability both in vitro and in vivo. In vitro cellular uptake and in vivo small animal PET imaging revealed the probe binding to PD-L1 with high affinity and specificity, consistent with the results of immunofluorescence and immunohistochemistry. In the clinical study involving 15 participants, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P was proven safe with demonstrating low uptake in normal organs and physiologically excreting via the urinary system. Lung cancer patients with high PD-L1 expression (TPS 70-90%) exhibited higher tumor uptake and tumor-to-background ratios than those with negative or low PD-L1 expression (TPS < 1-10%), with SUVmax of 1.89-2.27 vs. 0.87-1.01, tumor-to-lung ratios of 4.73-7.68 vs. 1.61-2.35, and tumor-to-muscle ratios of 6.73-12.61 vs. 4.35-5.61.

CONCLUSION

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P showed promising as a PET agent to assess tumor PD-L1 expression in preclinical and first-in-human studies, offering a non-invasive, real-time and accurate tool to address clinical challenges in predicting and assessing the efficacy of immunotherapy.

Demystifying the Role of Immuno PET-CT in Non-Small Cell Lung Cancer: Clinical Value and Research Trends

The management of Lung cancer, especially non-small cell lung cancer has undergone a paradigm shift recently with the advent of new treatment approaches including focused radiotherapy as well as evolution of a newer class of immunotherapy agents. Treatment efficacy and survival rates have improved and it is now even more important that patients are selected for appropriate interventions on the basis of a comprehensive assessment including a range of imaging as well as in-vitro tests such as immunohistochemistry. A new class of tracers targeting programmed cell death such as PD1 and PDL1 (broadly classed as Immuno PET) are being increasingly used in the molecular characterisation of patients deemed resistant to standard treatment approaches and being considered for additional interventions such as immunotherapy. In this review, we review the latest evidence in the field and propose a summary of clinical usefulness and provide a review of the research trends in this exciting and evolving field.

Advances of PET/CT in Target Delineation of Lung Cancer Before Radiation Therapy

In the clinical management of lung cancer, radiotherapy remains a cornerstone of multimodal treatment strategies, often used alongside surgery or in combination with systemic therapies such as chemotherapy, tyrosine kinase inhibitors, and immune checkpoint inhibitors. While conventional imaging modalities like computed tomography (CT) and magnetic resonance imaging (MRI) continue to play a central role in staging, response assessment, and radiotherapy planning, advanced imaging techniques, particularly [18F]FDG PET/CT, are being increasingly integrated into routine clinical practice. These advanced techniques address the limitations of standard imaging by providing insight into molecular and metabolic tumor characteristics, enabling precise tumor visualization, accurate target volume delineation, and early treatment response assessment. This review examines the role of radiotherapy in the multidisciplinary management of lung cancer, detailing current concepts of morphological and functional imaging for staging and treatment planning. It also highlights the growing importance of PET-based radiotherapy planning, emphasizing its contributions to target volume definition and predictive value for treatment outcomes. Recent methodological advances, including the integration of artificial intelligence (AI), radiomics, technical innovations, and novel PET ligands, are discussed, highlighting their potential to improve the precision, efficacy, and personalization of lung cancer radiotherapy planning.

The Role of [18F]FDG PET/CT in Monitoring of Therapy Response in Lung Cancer

Lung cancer remains a leading cause of cancer deaths worldwide, with an all stage 5-year relative survival rate of less than 30%. Multiple treatment strategies are available and continue to evolve, with therapy primarily tailored to the type and stage of the disease. Accurate monitoring of therapy response is crucial for optimizing treatment outcomes. PET/CT imaging with [18F]FDG has become the standard of care across various phases of lung cancer management due to its ability to assess metabolic activity. This review underscores the pivotal role of [18F]FDG PET/CT in evaluating therapy response in lung cancer, particularly in non-small cell lung cancer (NSCLC). It examines conventional response criteria and their adaptations in the era of immunotherapy, highlighting the value of integrating metabolic imaging with established criteria to improve treatment assessment and guide clinical decisions. The potential of non-[18F]FDG PET tracers targeting diverse biological pathways to provide deeper insights into tumor biology, therapy response and predictive outcomes is also explored. Additionally, the emerging role of radiomics in enhancing treatment efficacy assessment and improving patient management is briefly highlighted. Despite the challenges in the routine clinical application of various metabolic response criteria, [18F]FDG PET/CT remains a crucial tool in monitoring therapy response in lung cancer. Ongoing advancements in therapeutic strategies, radiopharmaceuticals, and imaging techniques continue to drive progress in lung cancer management, promising improved patient outcomes.

Development and First-in-Human evaluation of a Site-Specific [18F]-Labeled PD-L1 nanobody PET radiotracer for noninvasive imaging in NSCLC

Immunohistochemistry (IHC) for PD-L1 detection is limited by its invasiveness and heterogeneity of tumors. To address these challenges, a new PD-L1-targeted nanobody-based immune-PET radiotracer [18F]AlF-APN09 was developed using the site-specific radiolabeling method with the complexing agent (Mal-RESCA) under mild conditions. [18F]AlF-APN09 was prepared at room temperature (pH 4.6-4.8) within 20 min with satisfactory radiochemical yields (45.8 ± 4.48 %, non-decay corrected), high radiochemical purity (>98 %) and moderate apparent molar activity (15-35 GBq/μmol), and remained stable in both PBS and 5 % HSA after 4 h (>90 %). Cell uptake studies indicated variable levels of surface PD-L1 expression in the following order: A549PD-L1 > H1975 > A549. In micro-PET/CT imaging, A549PD-L1 and H1975 tumors were distinctly visualized in a 6.0:1 and 3.2:1 ratios over PD-L1-negative A549 tumors in vivo. Ex vivo biodistribution studies showed tumor uptake values of 6.47 ± 1.06 %ID/g (A549PD-L1) and 2.27 ± 0.19 %ID/g (H1975), significantly higher than 0.90 ± 0.28 %ID/g in A549 tumors. The estimated effective radiation dose in humans was 8.65E-03 mSv/MBq, lower than that of conventional [18F]FDG. First-in-human imaging was conducted on a single resectable non-small cell lung cancer (NSCLC) subject without any adverse reactions. The radiotracer exhibited renal excretion with minimal hepatobiliary clearance. Tumor uptake reached SUVmax 4.20 at 2 h post-injection, demonstrating high contrast and rapid clearance. After PD-1 inhibitor immunotherapy and chemotherapy, the subject showed a therapeutic response and postoperative pathological specimens confirmed a major pathological response (MPR). These results suggest that we have successfully developed a new PD-L1-targeted nanobody PET tracer using the site-specific labeling method with the complexing agent (Mal-RESCA) within 20 min under mild conditions and [18F]AlF-APN09 is a promising noninvasive PET radiotracer for visualizing PD-L1 expression in tumors, offering rapid tumor targeting, excellent signal-to-noise ratios, and favorable clearance properties.

Imaging antigen processing and presentation in cancer

Introduction

Antigen processing and presentation are vital processes of the adaptive immunity. These processes involve a series of intracellular and extracellular events, including the enzymology within cells during antigen processing, the loading and presentation of antigenic peptides on major histocompatibility complexes, the recruitment of T cells, their interaction with antigen-presenting cells, and the expression of adhesion, co-stimulatory and co-inhibitory molecules at the T cell immunological synapse. These events collectively fine-tune and sustain antigen recognition and T cell function. Dysregulation of this machinery can profoundly impact the efficacy of cancer immunotherapy. Imaging technologies have emerged as powerful tools for elucidating the mechanisms underlying antigen processing and presentation. By providing complementary perspectives into the cellular and molecular interactions at play, imaging has significantly enhanced our understanding of these complex immunological events in cancer. Such insights can improve the monitoring of immunotherapy responses, facilitate the identification of effective treatments, and aid in predicting patient outcomes.

Methods

This review explores the role of imaging in studying antigen processing and presentation in the context of cancer.

Conclusion

It highlights key considerations for developing imaging tools and biomarkers to detect components of these pathways. Additionally, it examines the strengths and limitations of various imaging approaches and discusses their potential for clinical translation.

Discordant Responses Between Imaging Examination and Surgical Pathology of Head and Heck Squamous Cell Carcinoma After Neoadjuvant Immunotherapy Combined With Chemotherapy

Background

We here investigated the value of imaging examination in evaluating tumor remission-based surgery in patients with head and neck squamous cell carcinoma (HNSCC), who had undergone neoadjuvant immunotherapy combined with chemotherapy (NICC).

Methods

HNSCC patients who underwent NICC and surgery from May 2021 to September 2023 were retrospectively analyzed. All patients had to undergo imaging examination evaluation, including enhanced computed tomography (CT) and enhanced magnetic resonance (MR) imaging before and after NICC. Data related to clinical parameters, complete response of the primary site (PrCR), complete response of the primary site and the lymph node (PLCR), complete response of the lymph node (LCR), and tumor response (TR), were gathered. The paired Chi-square test and t-test were conducted to analyze the differences in responses between imaging examination and pathology. Binary logistic regression was applied to analyze the relevant clinical factors of differences in responses.

Results

In total, data of 41 patients were included in this study. Significant discordant responses were observed between enhanced CT, magnetic resonance imaging (MRI), and pathology in PrCR (4.9%, 7.3% vs. 41.5%), LCR (12.2%, 7.3% vs. 53.7%), PLCR (0%, 0% vs. 31.7%), and TR (severe 29.3%,17.1% vs. 25.61%) (P < 0.05). Patients with hypopharyngeal cancer (odds ratio (OR): 7.04), oral cancer (OR: 3.64), higher neutrophil to lymphocyte ratio (NLR) (OR: 2.05), and earlier T stage (OR: 0.71) exhibited a larger response difference between enhanced CT and pathology. Patients with younger age (OR: 0.79) hypopharyngeal cancer (OR: 22.81), oral cancer (OR: 2.65), higher NLR (OR: 19.47), and earlier T stage (OR: 0.29) exhibited a larger response difference between enhanced MR and pathology.

Conclusions

Discordant responses were noted between the imaging examination and surgical pathology of HNSCC after NICC. Hypopharyngeal cancer, higher NLR, and earlier T stage may predict a higher response difference.

Nuclear Molecular Imaging for Evaluating T Cell Exhaustion

T cells are indispensable for the therapeutic efficacy of cancer immunotherapies, including immune checkpoint blockade. However, prolonged antigen exposure also drives T cells into exhaustion, which is characterized by upregulated inhibitory molecules, impaired effector functions, reduced cytotoxicity, altered metabolism, etc. Noninvasive monitoring of T cell exhaustion allows a timely identification of cancer patients that are most likely to benefit from immunotherapies. In this Review, we briefly explain the biological cascades underlying the modulation of inhibitory molecules, present a concise update on the nuclear molecular imaging tracers of T cell exhaustion, and then discuss the potential opportunities for future development.

Novel Peptide-Based 68Ga-Labeled Radiotracer for Preclinical Studies of TIM3 Expression

T-cell immunoglobulin and mucin domain-3 (TIM3) is an immune checkpoint that plays a negative regulatory role in the immune response. TIM3-targeted drugs inhibit this negative regulation, thereby modulating the level of immune response activation. In the previous investigation, several peptides targeting TIM3 were identified through screening from a phage peptide library. In this research, three peptides were selected to construct the radioactive molecular probes according to the characteristic that targeting TIM3 drugs would lead to the increase of interferon-γ (IFN-γ) secretion. Molecular docking was performed to assess the binding properties of the selected peptides with the TIM3 protein. To further enhance the targeting properties, one of the peptides with a higher-affinity peptide was structurally modified. Then, 68Ga was used to construct the peptide probe 68Ga-DOTA-peptide by labeling the six peptides with 68Ga riboprobes, and the binding affinity and specificity were assessed using TIM3 overexpressing cell line A549TIM3 and the parental A549 cells. In addition, in Micro-PET/CT imaging, transfected model mice were dynamically imaged for 30 min after injection of 3.7-7.4 MBq 68Ga-DOTA-peptides via the tail vein. Meanwhile, the same dose of molecular probes was injected in the MC38 model (colorectal cancer in mice) and the CCRCC (clear cell renal cell carcinoma) xenografted model, followed by static scans at 15, 30, and 60 min postinjection. Finally, immunohistochemical (IHC) staining was performed to assess TIM3 expression in the dissected tumor tissues. The molecular docking results showed that the binding energy of P26 to TIM3 protein was -6.5 kcal/mol, which was lower than that of P24 to TIM3 protein, -3.6 kcal/mol, indicating that the affinity of P26 peptide to TIM3 protein was higher than that of P24 and P20 peptide. After structural modification of the P26 peptide, P26NH2, r-NH2, and P26X2 were obtained, and the above peptides were successfully constructed into six targeting TIM3 peptide probes by 68Ga labeling. Cellular uptake experiments demonstrated that 68Ga-DOTA-P26, 68Ga-DOTA-P26NH2, and 68Ga-DOTA-r-NH2 showed significantly higher uptake in A549TIM3 cells than in A549 cells and could be blocked by the unlabeled peptide. Micro-PET imaging experiments showed that the uptake of each probe in the A549TIM3 model tumor tissue was significantly higher than that in the A549 model tumor tissue, and a comparison of the tumor-to-cardiac uptake ratios of each group showed that the 68Ga-DOTA-P26 had a better tumor-to-cardiac uptake ratio in the A549TIM3 model than several other molecular probes, and in the MC38 model, similar results were obtained, with the difference that the 68Ga-DOTA-P26NH2 had the highest tumor-to-cardiac uptake ratio in the CCRCC model. Finally, validation by IHC showed that A549TIM3, MC38, and CCRCC tumor tissues had varying degrees of TIM3 expression. Upon comparison of ex vivo and in vivo studies, one of them, the 68Ga-DOTA-P26 probe, demonstrated significant target specificity for TIM3. These results suggest that studying peptide probes targeting TIM3 will promote the process of TIM3-targeted drug research and is expected to guide the application of TIM3 immune checkpoint drugs in immunotherapy.

Comprehensive Potential of Artificial Intelligence for Predicting PD-L1 Expression and EGFR Mutations in Lung Cancer: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the methodological quality and the predictive performance of artificial intelligence (AI) for predicting programmed death ligand 1 (PD-L1) expression and epidermal growth factor receptors (EGFR) mutations in lung cancer (LC) based on systematic review and meta-analysis.

METHODS

AI studies based on PET/CT, CT, PET, and immunohistochemistry (IHC)-whole-slide image (WSI) were included to predict PD-L1 expression or EGFR mutations in LC. The modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to evaluate the methodological quality. A comprehensive meta-analysis was conducted to analyze the overall area under the curve (AUC). The Cochrane diagnostic test and I2 statistics were used to assess the heterogeneity of the meta-analysis.

RESULTS

A total of 45 AI studies were included, of which 10 were used to predict PD-L1 expression and 35 were used to predict EGFR mutations. Based on the analysis using the QUADAS-2 tool, 37 studies achieved a high-quality score of 7. In the meta-analysis of PD-L1 expression levels, the overall AUCs for PET/CT, CT, and IHC-WSI were 0.80 (95% confidence interval [CI], 0.77-0.84), 0.74 (95% CI, 0.69-0.77), and 0.95 (95% CI, 0.93-0.97), respectively. For EGFR mutation status, the overall AUCs for PET/CT, CT, and PET were 0.85 (95% CI, 0.81-0.88), 0.83 (95% CI, 0.80-0.86), and 0.75 (95% CI, 0.71-0.79), respectively. The Cochrane Diagnostic Test revealed an I2 value exceeding 50%, indicating substantial heterogeneity in the PD-L1 and EGFR meta-analyses. When AI was combined with clinicopathological features, the enhancement in predicting PD-L1 expression was not substantial, whereas the prediction of EGFR mutations showed improvement compared to the CT and PET models, albeit not significantly so compared to the PET/CT models.

CONCLUSIONS

The overall performance of AI in predicting PD-L1 expression and EGFR mutations in LC has promising clinical implications.

First-in-Human Study of 23ME-00610, an Antagonistic Antibody for Genetically Validated CD200R1 Immune Checkpoint, in Participants with Advanced Solid Malignancies

PURPOSE

In this phase 1 portion of a first-in-human phase 1/2a study (NCT05199272), 23ME-00610 was evaluated in participants with advanced solid malignancies to determine its safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD). Exploratory biomarkers were evaluated to examine potential correlates of efficacy and safety.

PATIENTS AND METHODS

Eligible participants (≥18 years) were administered 23ME-00610 intravenously every 3 weeks (Q3W) using an accelerated titration design followed by a traditional 3 + 3 design, with an initial dose level of 2 mg.

RESULTS

Twenty-eight participants were enrolled across seven cohorts and received a median of four cycles of 23ME-00610. No treatment-related serious adverse events (AE) were observed, and the maximum tolerated dose was not reached. Overall, the PK of 23ME-00610 was linear and dose proportional for doses ≥60 mg, with a median terminal half-life of 13 days at 1,400 mg. Peripheral saturation of CD200R1 was observed for doses ≥60 mg. Immune-related AEs, including rash, pruritus, and hypothyroidism, were predicted by phenome-wide association studies and observed for doses ≥60 mg. A confirmed partial response was observed in a participant with well-differentiated pancreatic neuroendocrine cancer whose tumor was among those with the highest tumor CD200 expression.

CONCLUSIONS

23ME-00610 has mild-to-moderate on-target AEs and PK/PD consistent with tumor target saturation and dosing every 3 weeks. The trend for clinical benefit in participants with tumor CD200 expression suggests that 23ME-00610 inhibits CD200R1 signaling and may reverse CD200-mediated immune evasion. Based on PK/PD, safety, and preliminary antitumor activity, 1,400 mg Q3W was selected as the dose for further study.

SIGNIFICANCE

Genome-wide association studies (GWAS) of the 23andMe genetic database identified CD200R1 as a promising therapeutic target for cancer. This phase 1 study of 23ME-00610, a CD200R1 antagonist IgG1, showed acceptable safety and tolerability, PK supporting Q3W dosing, and PD and preliminary clinical activity supporting an initial recommended phase 2 dose of 1,400 mg.

Multimodal Imaging Approach for Tumor Treatment Response Evaluation in the Era of Immunotherapy

ABSTRACT

Immunotherapy is likely the most remarkable advancement in lung cancer treatment during the past decade. Although immunotherapy provides substantial benefits, their therapeutic responses differ from those of conventional chemotherapy and targeted therapy, and some patients present unique immunotherapy response patterns that cannot be judged under the current measurement standards. Therefore, the response monitoring of immunotherapy can be challenging, such as the differentiation between real response and pseudo-response. This review outlines the various tumor response patterns to immunotherapy and discusses methods for quantifying computed tomography (CT) and 18 F-fluorodeoxyglucose positron emission tomography (PET) in the field of lung cancer. Emerging technologies in magnetic resonance imaging (MRI) and non-FDG PET tracers are also explored. With immunotherapy responses, the role for imaging is essential in both anatomical radiological responses (CT/MRI) and molecular changes (PET imaging). Multiple aspects must be considered when assessing treatment responses using CT and PET. Finally, we introduce multimodal approaches that integrate imaging and nonimaging data, and we discuss future directions for the assessment and prediction of lung cancer responses to immunotherapy.

The State-of-the-Art PET Tracers in Glioblastoma and High-grade Gliomas and Implications for Theranostics

MR imaging is currently the main imaging modality used for the diagnosis and post therapeutic assessment of glioblastomas. Recently, several innovative PET radioactive tracers have been investigated for the evaluation of glioblastomas (GBM). These radiotracers target several biochemical and pathophysiological processes seen in tumors. These include glucose metabolism, DNA synthesis and cell proliferation, amino acid transport, cell membrane biosynthesis, specific membrane antigens such as prostatic specific membrane antigens, fibroblast activation protein inhibitor, translocator protein and hypoxia sensing agents, and antibodies targeting specific cell receptor antigen. This review aims to discuss the clinical value of these PET radiopharmaceuticals in the evaluation and treatment of GBMs.

Non-[18F]FDG PET-Radiopharmaceuticals in Oncology

Molecular imaging is a growing field, driven by technological advances, such as the improvement of PET-CT scanners through the introduction of digital detectors and scanners with an extended field of view, resulting in much higher sensitivity and a variety of new specific radiopharmaceuticals that allow the visualization of specific molecular pathways and even theragnostic approaches. In oncology, the development of dedicated tracers is crucial for personalized therapeutic approaches. Novel peptides allow the visualization of many different targets, such as PD-1 and PD-L1 expression, chemokine expression, HER expression, T-cell imaging, microenvironmental imaging, such as FAP imaging, and many more. In this article, we review recent advances in the development of non-[18F]FDG PET radiopharmaceuticals and their current clinical applications in oncology, as well as some future aspects.

Development of selective ssDNA micro-probe for PD1 detection as a novel strategy for cancer imaging

Programmed death receptor 1, PD1, modulates the function of immune cells by providing inhibitory signals and constitutes the marker of immune exhaustion. Monitoring the level of PD1 promises a useful diagnostic approach in autoimmune diseases and cancer. Here we describe the development of an ssDNA aptamer-based molecular probe capable of specific recognition of human PD1 receptor. The aptamer was selected using SELEX, its sequence was further optimized, and the affinity and specificity were determined in biochemical assays. The aptamer was converted into a fluorescent probe and its potential in molecular imaging was demonstrated in a culture of human cells overexpressing PD1 and murine pancreatic organoids / immune cells mixed co-culture model. We conclude that the provided aptamers are suitable probes for imaging of PD1 expressing immune cells even in complex cellular models and may find future utility as diagnostic tools.

Molecular imaging of renal cell carcinomas: ready for prime time

The clinical diagnosis of renal cell carcinoma (RCC) is constantly evolving. Diagnostic imaging of RCC relying on enhanced computed tomography (CT) and magnetic resonance imaging (MRI) is commonly used for renal mass characterization and assessment of tumour thrombosis, whereas pathology is the gold standard for establishing diagnosis. However, molecular imaging is rapidly improving the clinical management of RCC, particularly clear-cell RCC. Molecular imaging aids in the non-invasive visualization and characterization of specific biomarkers such as carbonic anhydrase IX and CD70 within the tumours, which help to assess tumour heterogeneity and status. Target-specific molecular imaging of RCCs will substantially improve the diagnostic landscape of RCC and will further facilitate clinical decision-making regarding initial staging and re-staging, monitoring of recurrence and metastasis, patient stratification and selection, and the prediction and evaluation of treatment responses.

Current and Future Perspectives of PDL1 PET and SPECT Imaging

Programmed Death 1 (PD1) and Programmed Death Ligand (PDL1) play a crucial role in tumor microenvironment by helping cancer cells evade innate immunity. Numerous inhibitor anticancer drugs targeting this interplay have been used in clinical practice and many more are in preclinical stage. These drugs have shown promising results in achieving good response and long-term clinical benefit, is routinely performed to identify patients who may benefit. However, there are major challenges associated with these immunohistochemistry tests which have opened the space for noninvasive imaging modalities using PD1 and PDL1 inhibitors labeled with either PET or SPECT radionuclides. These radiopharmaceuticals, although primarily developed for the field of immunotherapy, have great potential in expanding and optimizing the combination of radiopharmaceutical therapies with PD1-PDL1 targeting anticancer drugs. This review elaborates currently available PET and SPECT radiopharmaceuticals targeting PD1-PDL1 axis. It also explores the potential future role of newer targets which are being developed and tested in various preclinical studies.

Noninvasive Monitoring of Programmed Death-Ligand 2 Expression with Positron Emission Tomography using 68Ga-labeled Peptide Antagonist in Preclinical and Exploratory Human Studies

While the expression of programmed death ligand-1 (PD-L1) is associated with response to immune therapy, PD-L1-negative patients may still benefit from immune treatment. Programmed death ligand-2 (PD-L2), another crucial immune checkpoint molecule interacting with PD-1, correlates with the efficacy of various tumor immune therapies. This study investigates the expression of PD-L2 in non-small cell lung cancer (NSCLC) patients following anti-PD-1 therapy and its predictive value for clinical survival outcomes. Additionally, we explore the noninvasive, real-time, and dynamic quantitative analysis potential of PD-L2 positron emission tomography (PET) imaging in transplanted tumors. We utilized [68Ga]Ga-labeled peptide HN11-1 for PD-L2 PET imaging. The results indicate a higher response rate to anti-PD-1 therapy in patients positive for both PD-L1 and PD-L2, with PD-L2 status independently predicting progression-free survival (PFS) with pembrolizumab treatment. Furthermore, [68Ga]Ga-HN11-1 PET imaging demonstrates specificity in assessing PD-L2 status. Overall, we confirm the correlation between high PD-L2 expression and favorable PFS in NSCLC patients post anti-PD-1 therapy and highlight the promising potential of [68Ga]Ga-HN11-1 as a specific tracer for PD-L2 in preclinical and initial human trials.

Recent Updates of PET in Lymphoma: FDG and Beyond

Lymphoma is one of the most common cancers worldwide, categorized into Hodgkin lymphoma and non-Hodgkin lymphoma. 18F-fluorodeoxyglucose positron emission tomography (FDG PET) has become an essential imaging tool for evaluating patients with lymphoma in terms of initial diagnosis, staging, prognosis, and treatment response assessment. Recent advancements in imaging technology and methodologies, along with the development of artificial intelligence, have revolutionized the evaluation of complex imaging data, enhancing the diagnostic and predictive power of PET in lymphoma. However, FDG is not cancer-specific, but it primarily reflects glucose metabolism, which has prompted the investigation of alternative PET tracers to address this limitation. Novel PET radiotracers, such as fibroblast activation protein inhibitors targeting the tumor microenvironment, have recently shown promising results in evaluating various malignancies compared to FDG PET. Furthermore, with the rapid advancements in immunotherapy and the favorable imaging properties of 89Zr, immunoPET has emerged as a promising modality, offering insights into the functional and molecular status of the immune system. ImmunoPET can also facilitate the development of new antibody therapeutics and radioimmunotherapy by providing pharmacokinetic and pharmacodynamic data. This review provides comprehensive insights into the current clinical applications of FDG PET in lymphoma, while also exploring novel PET imaging radiotracers beyond FDG, discussing their mechanisms of action and potential impact on patient management.

New PET Tracers for Lymphoma

While functional imaging with [18F]Fluoro-deoxy-glucose positron emission tomography (PET)/computed tomography is a well-established imaging modality in most lymphoma entities, novel tracers addressing cell surface receptors, tumor biology, and the microenvironment are being developed. Especially, with the emergence of immuno-PET targeting surface markers of lymphoma cells, a new imaging modality of immunotherapies is evolving, which might especially aid in relapsed and refractory disease stages. This review highlights different new PET tracers in indolent and aggressive lymphoma subtypes and summarizes the current state of immuno-PET imaging in lymphoma.

Next Generation of Solid Target Radionuclide Antibody Conjugates for Tumor Immuno-Therapy

Immune checkpoint therapy has emerged as an effective treatment option for various types of cancers. Key immune checkpoint molecules, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and lymphocyte activation gene 3 (LAG-3), have become pivotal targets in cancer immunotherapy. Antibodies designed to inhibit these molecules have demonstrated significant clinical efficacy. Nevertheless, the ability to monitor changes in the immune status of tumors and predict treatment response remains limited. Conventional methods, such as assessing lymphocytes in peripheral blood or conducting tumor biopsies, are inadequate for providing real-time, spatial information about T-cell distributions within heterogeneous tumors. Positron emission tomography (PET) using T-cell specific probes represents a promising and noninvasive approach to monitor both systemic and intratumoral immune changes during treatment. This technique holds substantial clinical significance and potential utility. In this paper, we review the applications of PET probes that target immune cells in molecular imaging.

Prediction of programmed death-1 expression status in non-small cell lung cancer based on intratumoural and peritumoral computed tomography (CT) radiomics nomogram

AIMS

This study aimed to predict the expression of programmed death-1 (PD-1) in non-small cell lung cancer (NSCLC) using intratumoral and peritumoral computed tomography (CT) radiomics nomogram.

MATERIALS AND METHODS

Two hundred patients pathologically diagnosed with NSCLC from two hospitals were retrospectively analyzed. Of these, 159 NSCLC patients from our hospital were randomly divided into a training cohort (n=96) and an internal validation cohort (n=63) at a ratio of 6:4, while 41 NSCLC patients from another medical institution served as the external validation cohort. The radiomic features of the gross tumor volume (GTV) and peritumoral volume (PTV) were extracted from the CT images. Optimal radiomics features were selected using least absolute shrinkage and selection operator regression analysis. Finally, a CT radiomics nomogram of clinically independent predictors combined with the best rad-score was constructed.

RESULTS

Compared with the 'GTV' and 'PTV' radiomics models, the combined 'GTV + PTV' radiomics model showed better predictive performance, and its area under the curve (AUC) values in the training, internal validation, and external validation cohorts were 0.90 (95% confidence interval [CI]: 0.83-0.97), 0.85 (95% CI: 0.74-0.96) and 0.78 (95% CI: 0.63-0.92). The nomogram constructed by the rad-score of the 'GTV + PTV' radiomics model combined with clinical independent predictors (prealbumin and monocyte) had the best performance, with AUC values in each cohort being 0.92 (95% CI: 0.85-0.98), 0.88 (95% CI: 0.78-0.97), and 0.80 (95% CI: 0.66-0.94), respectively.

CONCLUSION

The intratumoral and peritumoral CT radiomics nomogram may facilitate individualized prediction of PD-1 expression status in patients with NSCLC.

Synthesis and evaluation of anti-PD-L1-B11 antibody fragments for PET imaging of PD-L1 in breast cancer and melanoma tumor models

There is a critical need to non-invasively assess the PD-L1 expression in tumors as a predictive biomarker for determining the efficacy of anti-PD-1/PD-L1 immunotherapies. Non-invasive imaging modality like positron emission tomography (PET) can be a powerful tool to assess the PD-L1 expression in the whole body including multiple metastases as a patient selection criterion for the anti-PD-1/PD-L1 immunotherapy. In this study, we synthesized B11-nanobody, B11-scFv and B11-diabody fragments from the full-length anti-PD-L1 B11 IgG. Out of the three antibody fragments, B11-diabody showed higher nM affinity towards PD-L1 antigen as compared to B11-scFv and B11-nanobody. All three antibody fragments were successfully radiolabeled with 64Cu, a PET radioisotope. For radiolabeling, the antibody fragments were first conjugated with p-SCN-Bn-NOTA followed by chelation with 64Cu. All three radiolabeled antibody fragments were found to be stable in mouse and human sera for up to 24 h. Additionally, all three [64Cu]Cu-NOTA-B11-antibody fragments were evaluated in PD-L1 negative and human PD-L1 expressing cancer cells and subcutaneous tumor models. Based on the results, [64Cu]Cu-NOTA-B11-diabody has potential to be used as a PET imaging probe for assessing PD-L1 expression in tumors as early as 4 h post-injection, allowing faster assessment compared to the full length IgG based PET imaging probe.

Radioimmunotheragnosis in Cancer Research

The combination of immunoPET-where an antibody (Ab) is labeled with an isotope for PET imaging-and radioimmunotherapy (RIT), using the same antibody with a therapeutic isotope, offers significant advantages in cancer management. ImmunoPET allows non-invasive imaging of antigen expression, which aids in patient selection for subsequent radioimmunotherapy. It also facilitates the assessment of tumor response to therapy, allowing for treatment adjustments if necessary. In addition, immunoPET provides critical pharmacokinetic data, including antibody biodistribution and clearance rates, which are essential for dosimetry calculations and treatment protocol optimization. There are still challenges to overcome. Identifying appropriate target antigens that are selectively expressed on cancer cells while minimally expressed on normal tissues remains a major hurdle to reduce off-target toxicity. In addition, it is critical to optimize the pharmacokinetics of radiolabeled antibodies to maximize tumor uptake and minimize normal tissue uptake, particularly in vital organs such as the liver and kidney. This approach offers the potential for targeted and personalized cancer therapy with reduced systemic toxicity by exploiting the specificity of monoclonal antibodies and the cytotoxic effects of radiation. However, further research is needed to address remaining challenges and to optimize these technologies for clinical use.

Factors Affecting an Increase in Spleen Volume and Association of Spleen Volume Variation with the Clinical Outcomes of Atezolizumab and Bevacizumab Treatment for Hepatocellular Carcinoma: A Retrospective Analysis

INTRODUCTION

Gastrointestinal varices rupture is considered to be prone to occur during atezolizumab and bevacizumab (Atez/Bev) treatment. This study aimed to investigate predictive factors affecting the increase in spleen volume (SpV) and the association of SpV variation with the clinical outcomes of Atez/Bev.

METHODS

A total of 164 HCC patients were included in this retrospective multicenter study. We measured SpV based on CT scans obtained before treatment and at evaluations. We used the inverse probability of treatment weight to address the imbalance between patient characteristics.

RESULTS

The median pretreatment SpV was 184 (130-257) cm3 and the median SpV variation was 27 (9-60) cm3. An increase in the SpV was observed in 140 patients (85.4%). Age <74 years (p = 0.03), mALBI grade 2b or 3 (p = 0.03), and pretreatment SpV ≥184 cm3 (p < 0.001) were significantly associated with increased SpV. There were no significant differences in progression-free survival (PFS) or overall survival (OS) between patients with SpV variation <25 cm3 and those with SpV variation ≥25 cm3 in the crude (p = 0.3 and 0.7) and IPTW-weighted cohorts (p = 0.08 and 0.8, respectively). Regarding pretreatment SpV, there were no significant differences in PFS or OS between patients with and without pretreatment spleen enlargement in the crude (both p = 0.3) and IPTW-weighted cohort (p = 0.6 and 0.3, respectively).

CONCLUSION

Caution is warranted to detect the aggravation of portal hypertension when administering Atez/Bev to young patients or patients with an impaired liver function or pretreatment spleen enlargement. The impact of spleen modulation by Atez/Bev appears to be limited on clinical efficacy.

In-depth cross-validation of human and mouse CD4-specific minibodies for noninvasive PET imaging of CD4+ cells and response prediction to cancer immunotherapy

Increasing evidence emphasizes the pivotal role of CD4+ T cells in orchestrating cancer immunity. Noninvasive in vivo imaging of the temporal dynamics of CD4+ T cells and their distribution patterns might provide novel insights into their effector and regulator cell functions during cancer immunotherapy (CIT). Methods: We conducted a comparative analysis of 89Zr-labeled anti-mouse (m) and anti-human (h) CD4-targeting minibodies (Mbs) for in vivo positron emission tomography (PET)/magnetic resonance imaging (MRI) of CD4+ T cells in human xenografts, syngeneic tumor-bearing wild-type (WT), and human CD4+ knock-in (hCD4-KI) mouse models. Results: Both 89Zr-CD4-Mbs yielded high radiolabeling efficiencies of >90%, immunoreactivities of >70%, and specific in vitro binding to their target antigens. The specificity of in vivo targeting of 89Zr-hCD4-Mb was confirmed by PET/MRI, revealing ~4-fold greater 89Zr-hCD4-Mb uptake in subcutaneous hCD4+ hematopoietic peripheral blood acute lymphoblastic leukemia tumors (HPB-ALL) than in solid hCD4- diffuse histiocytic lymphomas (DHL) and 89Zr-mCD4-Mb uptake in hCD4+ HPB-ALL tumors. In a comparative cross-validation study in anti-programmed death ligand (αPD-L1)/anti-4-1BB-treated orthotopic PyMT mammary carcinoma-bearing hCD4-KI and WT mice, we detected 2- to 3-fold enhanced species-specific 89Zr-hCD4-Mb or 89Zr-mCD4-Mb uptake within CD4+ cell-enriched secondary lymphatic organs (lymph nodes and spleens). The 89Zr-hCD4-Mb uptake in the PyMT tumors was more pronounced in hCD4-KI mice compared to the WT control littermates. Most importantly, MC38 adenocarcinoma-bearing mice treated with a combination of αPD-L1 and anti-lymphocyte-activation gene 3 (αLag-3) antibodies exhibited ~1.4-fold higher 89Zr-mCD4-Mb uptake than mice that were not responsive to therapy or sham-treated mice. Conclusion: CD4 PET/MRI enabled monitoring of the CD4+ cell distribution in secondary lymphatic organs and the tumor microenvironment, capable of predicting sensitivity to CIT. Our imaging approach will provide deeper insights into the underlying molecular mechanisms of CD4-directed cancer immunotherapies in preclinical mouse models and is applicable for clinical translation.

Circulating T cell status and molecular imaging may predict clinical benefit of neoadjuvant PD-1 blockade in oral cancer

BACKGROUND

Addition of neoadjuvant immune checkpoint inhibition to standard-of-care interventions for locally advanced oral cancer could improve clinical outcome.

METHODS

In this study, 16 evaluable patients with stage III/IV oral cancer were treated with one dose of 480 mg nivolumab 3 weeks prior to surgery. Primary objectives were safety, feasibility, and suitability of programmed death receptor ligand-1 positron emission tomography (PD-L1 PET) as a biomarker for response. Imaging included 18F-BMS-986192 (PD-L1) PET and 18F-fluorodeoxyglucose (FDG) PET before and after nivolumab treatment. Secondary objectives included clinical and pathological response, and immune profiling of peripheral blood mononuclear cells (PBMCs) for response prediction. Baseline tumor biopsies and postnivolumab resection specimens were evaluated by histopathology.

RESULTS

Grade III or higher adverse events were not observed and treatment was not delayed in relation to nivolumab administration and other study procedures. Six patients (38%) had a pathological response, of whom three (19%) had a major (≥90%) pathological response (MPR). Tumor PD-L1 PET uptake (quantified using standard uptake value) was not statistically different in patients with or without MPR (median 5.3 vs 3.4). All major responders showed a significantly postnivolumab decreased signal on FDG PET. PBMC immune phenotyping showed higher levels of CD8+ T cell activation in MPR patients, evidenced by higher baseline expression levels of PD-1, TIGIT, IFNγ and lower levels of PD-L1.

CONCLUSION

Together these data support that neoadjuvant treatment of advanced-stage oral cancers with nivolumab was safe and induced an MPR in a promising 19% of patients. Response was associated with decreased FDG PET uptake as well as activation status of peripheral T cell populations.

Illuminating immunotherapy response via precision T cell-targeted PET imaging

Traditionally, immunotherapy agent selection and treatment strategies are guided by biopsy-based histological information. However, biopsies are limited in that they are invasive, provide static information regarding the tumor immune microenvironment, and only sample a small part of one tumor site. The tumor microenvironment is dynamic and heterogenous. As a result, the immune milieu at one site may be distinct from other metastatic sites. These factors make identifying which patients are likely to respond to different immunotherapies and which harbor intrinsic resistance mechanisms difficult to identify based on a biopsy alone. As such, there is significant interest in alternative methodologies that better characterize the tumor immune microenvironment and monitor immunotherapy response. PET imaging potentially offers a non-invasive way to characterize the tumor immune microenvironment at the primary tumor and metastases and allow for longitudinal characterization. Herein, we review pre-clinically and clinically tested T cell-targeted PET radiopharmaceuticals, as T cells have been the dominant immunotherapy target, and their utility in both evaluating response to immunotherapy and in understanding the systemic immune response to treatment with immunotherapeutics.

AUNP-12 Near-Infrared Fluorescence Probes across NIR-I to NIR-II Enable In Vivo Detection of PD-1/PD-L1 Axis in the Tumor Microenvironment

The innovative PD-1/PD-L1 pathway strategy is gaining significant traction in cancer therapeutics. However, fluctuating response rates of 20-40% to PD-1/PD-L1 inhibitors, coupled with the risk of hyperprogression after immunotherapy, underscore the need for accurate patient selection and the identification of more beneficiaries. Molecular imaging, specifically near-infrared (NIR) fluorescence imaging, is a valuable alternative for real-time, noninvasive visualization of dynamic PD-L1 expression in vivo. This research introduces AUNP-12, a novel PD-L1-targeting peptide antagonist conjugated with Cy5.5 and CH1055 for first (NIR-I) and second near-infrared (NIR-II) imaging. These probes have proven to be effective in mapping PD-L1 expression across various mouse tumor models, offering insights into tumor-immune interactions. This study highlights the potential of AUNP-12-Cy5.5 and AUNP-12-CH1055 for guiding clinical immunotherapy through precise patient stratification and dynamic monitoring, supporting the shift toward molecular imaging for personalized cancer care.

Exploring the predictive potential of programmed death ligand 1 expression in healthy organs and lymph nodes as measured by 18F-BMS986-192 PET: pooled analysis of data from four solid tumor types

INTRODUCTION

Immune checkpoint inhibitors (ICIs) can elicit anticancer immune responses, but predictive biomarkers are needed. We measured programmed death ligand 1 (PD-L1) expression in organs and lymph nodes using 18F-BMS-986192 positron emission tomography (PET)-imaging and looked for correlations with response and immune-related adverse events.

METHODS

Four 18F-BMS-986192 PET studies in patients with melanoma, lung, pancreatic and oral cancer, receiving ICI treatment, were combined. Imaging data (organ standardized uptake value (SUV)mean, lymph node SUVmax) and clinical data (response to treatment and incidence of immune-related adverse events) were extracted.

RESULTS

Baseline PD-L1 uptake in the spleen was on average higher in non-responding patients than in responders (spleen SUVmean 16.1±4.4 vs 12.5±3.4, p=0.02). This effect was strongest in lung cancer, and not observed in oral cancer. In the oral cancer cohort, benign tumor-draining lymph nodes (TDLNs) had higher PD-L1 uptake (SUVmax 3.3 IQR 2.5-3.9) compared with non-TDLNs (SUVmax 1.8, IQR 1.4-2.8 p=0.04). Furthermore, in the same cohort non-responders showed an increase in PD-L1 uptake in benign TDLNs on-treatment with ICIs (+15%), while for responders the PD-L1 uptake decreased (-11%). PD-L1 uptake did not predict immune-related adverse events, though elevated thyroid uptake on-treatment correlated with pre-existing thyroid disease or toxicity.

CONCLUSION

PD-L1 PET uptake in the spleen is a potential negative predictor of response to ICIs. On-treatment with ICIs, PD-L1 uptake in benign TDLNs increases in non-responders, while it decreases in responders, potentially indicating a mechanism for resistance to ICIs in patients with oral cancer.

PD-L1 has a heterogeneous and dynamic expression in gastric cancer with implications for immunoPET

Introduction

This study aimed to investigate the dynamics of programmed death-ligand 1 (PD-L1) expression, spatial heterogeneity, and binding affinity of FDA-approved anti-PD-L1 antibodies (avelumab and atezolizumab) in gastric cancer. Additionally, we determined how PD-L1 glycosylation impacts antibody accumulation in gastric cancer cells.

Methods

Dynamic PD-L1 expression was examined in NCIN87 gastric cancer cells. Comparative binding studies of avelumab and atezolizumab were conducted in gastric cancer models, both in vitro and in vivo. Antibody uptake in tumors was visualized through positron emission tomography (PET) imaging. PD-L1 glycosylation status was determined via Western blot analyses before and after PNGase F treatment.

Results

Consistent findings revealed time-dependent PD-L1 induction in NCIN87 gastric cancer cells and spatial heterogeneity in tumors, as shown by PET imaging and immunofluorescence. Avelumab displayed superior binding affinity to NCIN87 cells compared to atezolizumab, confirmed by in vivo PET imaging and ex vivo biodistribution analyses. Notably, PD-L1 glycosylation at approximately 50 kDa was observed, with PNGase F treatment inducing a shift to 35 kDa in molecular weight. Tissue samples from patient-derived xenografts (PDXs) validated the presence of both glycosylated and deglycosylated PD-L1 (degPD-L1) forms in gastric cancer. Immunofluorescence microscopy and binding assays demonstrated enhanced avelumab binding post-deglycosylation.

Discussion

This study provides an understanding of dynamic and spatially heterogeneous PD-L1 expression in gastric cancer. Anti-PD-L1 immunoPET was able to visualize gastric tumors, and PD-L1 glycosylation has significant implications for antibody recognition. These insights contribute to demonstrating the complexities of PD-L1 in gastric cancer, holding relevance for refining PD-L1 imaging-based approaches.

Navigating the landscape of PD-1/PD-L1 imaging tracers: from challenges to opportunities

Immunotherapy targeted to immune checkpoint inhibitors, such as the program cell death receptor (PD-1) and its ligand (PD-L1), has revolutionized cancer treatment. However, it is now well-known that PD-1/PD-L1 immunotherapy response is inconsistent among patients. The current challenge is to customize treatment regimens per patient, which could be possible if the PD-1/PD-L1 expression and dynamic landscape are known. With positron emission tomography (PET) imaging, it is possible to image these immune targets non-invasively and system-wide during therapy. A successful PET imaging tracer should meet specific criteria concerning target affinity, specificity, clearance rate and target-specific uptake, to name a few. The structural profile of such a tracer will define its properties and can be used to optimize tracers in development and design new ones. Currently, a range of PD-1/PD-L1-targeting PET tracers are available from different molecular categories that have shown impressive preclinical and clinical results, each with its own advantages and disadvantages. This review will provide an overview of current PET tracers targeting the PD-1/PD-L1 axis. Antibody, peptide, and antibody fragment tracers will be discussed with respect to their molecular characteristics and binding properties and ways to optimize them.

Consistency Analysis of Programmed Death Ligand 1 Expression in Non-Small Cell Lung Cancer Between Pleural Effusion and Matched Primary Lung Cancer Tissues by Immunohistochemical Double Staining

In clinical practice, programmed death ligand 1 (PD-L1) detection is prone to nonspecific staining due to the complex cellular composition of pleural effusion smears. In this study, diaminobenzidine (DAB) and 3-amino-9-ethylcarbazole (AEC) immunohistochemistry double staining was performed to investigate PD-L1 expression in tumor cells from malignant pleural effusion (MPE). MPE was considered as a metastasis in non-small cell lung cancer patients; thus, the heterogeneity between metastatic and primary lung cancer was revealed as well. Ninety paired specimens of MPE cell blocks and matched primary lung cancer tissues from non-small cell lung cancer patients were subjected to PD-L1 and thyroid transcription factor-1(TTF-1)/p63 immunohistochemistry double staining. Two experienced pathologists independently evaluated PD-L1 expression using 3 cutoffs (1%, 10%, and 50%). PD-L1 expression in MPE was strongly correlated with that in matched primary lung cancer tissues (R = 0.813; P < .001). Using a 4-tier scale (cutoffs: 1%, 10%, and 50%), the concordance was 71.1% (Cohen's κ = .534). Using a 2-tier scale, the concordance was 75.6% (1%, Cohen's κ = 0.53), 78.9% (10%, Cohen's κ = 0.574), and 95.6% (50%, Cohen's κ = 0.754). The rates of PD-L1 positivity in MPE (56.7%) were higher than that in lung tissues (32.2%). All 27 discordant cases had higher scores in MPE. The double-staining method provided superior identification of PD-L1-positive tumor cells on a background with nonspecific staining. In conclusion, PD-L1 expression was moderately concordant between metastatic MPE cell blocks and matched primary lung carcinoma tissues, with variability related to tumor heterogeneity. MPE should be considered to detect PD-L1 when histological specimens are unattainable, especially when PD-L1 expression is >50%. PD-L1 positivity rates were higher in MPE. Double staining can improve PD-L1 detection by reducing false-negative/positive results.

Brain metastasis: An insight into novel molecular targets for theranostic approaches

Brain metastases (BrM) are common malignant lesions in the central nervous system, and pose a significant threat in advanced-stage malignancies due to delayed diagnosis and limited therapeutic options. Their distinct genomic profiles underscore the need for molecular profiling to tailor effective treatments. Recent advances in cancer biology have uncovered molecular drivers underlying tumor initiation, progression, and metastasis. This, coupled with the advances in molecular imaging technology and radiotracer synthesis, has paved the way for the development of innovative radiopharmaceuticals with enhanced specificity and affinity for BrM specific targets. Despite the challenges posed by the blood-brain barrier to effective drug delivery, several radiolabeled compounds have shown promise in detecting and targeting BrM. This manuscript provides an overview of the recent advances in molecular biomarkers used in nuclear imaging and targeted radionuclide therapy in both clinical and preclinical settings. Additionally, it explores potential theranostic applications addressing the unique challenges posed by BrM.

The development process of 'fit-for-purpose' imaging biomarkers to characterize the tumor microenvironment

Immune-based treatment approaches are successfully used for the treatment of patients with cancer. While such therapies can be highly effective, many patients fail to benefit. To provide optimal therapy choices and to predict treatment responses, reliable biomarkers for the assessment of immune features in patients with cancer are of significant importance. Biomarkers (BM) that enable a comprehensive and repeatable assessment of the tumor microenvironment (TME), the lymphoid system, and the dynamics induced by drug treatment can fill this gap. Medical imaging, notably positron emission tomography (PET) and magnetic resonance imaging (MRI), providing whole-body imaging BMs, might deliver such BMs. However, those imaging BMs must be well characterized as being 'fit for purpose' for the intended use. This review provides an overview of the key steps involved in the development of 'fit-for-purpose' imaging BMs applicable in drug development, with a specific focus on pharmacodynamic biomarkers for assessing the TME and its modulation by immunotherapy. The importance of the qualification of imaging BMs according to their context of use (COU) as defined by the Food and Drug Administration (FDA) and National Institutes of Health Biomarkers, EndpointS, and other Tools (BEST) glossary is highlighted. We elaborate on how an imaging BM qualification for a specific COU can be achieved.

Cancer Immunotherapy and Medical Imaging Research Trends from 2003 to 2023: A Bibliometric Analysis

Purpose

With the rapid development of immunotherapy, cancer treatment has entered a new phase. Medical imaging, as a primary diagnostic method, is closely related to cancer immunotherapy. However, until now, there has been no systematic bibliometric analysis of the state of this field. Therefore, the main purpose of this article is to clarify the past research trajectory, summarize current research hotspots, reveal dynamic scientific developments, and explore future research directions.

Patients and Methods

A comprehensive search was conducted on the Web of Science Core Collection (WoSCC) database to identify publications related to immunotherapy specifically for the medical imaging of carcinoma. The search spanned the period from the year 2003 to 2023. Several analytical tools were employed. These included CiteSpace (6.2.4), and the Microsoft Office Excel (2016).

Results

By searching the database, a total of 704 English articles published between 2003 and 2023 were obtained. We have observed a rapid increase in the number of publications since 2018. The two most active countries are the United States (n=265) and China (n=170). Pittock, Sean J and Abu-sbeih, Hamzah are very concerned about the relationship between cancer immunotherapy and medical images and have published more academic papers (n = 5; n = 4). Among the top 10 co-cited authors, Topalian Sl (n=43) cited ranked first, followed by Graus F (n=40) cited. According to clustering, timeline, and burst word analysis, the results show that the current research focus is on "MRI", "deep learning", "tumor microenvironment" and so on.

Conclusion

Medical imaging and cancer immunotherapy are hot topics. The United States is the country with the most publications and the greatest influence in this field, followed by China. "MRI", "PET/PET-CT", "deep learning", "immune-related adverse events" and "tumor microenvironment" are currently hot research topics and potential targets.