PET/CT metabolic patterns in systemic immune activation: A new perspective on the assessment of immunotherapy response and efficacy

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

Complete and early response to cemiplimab associated to severe immune toxicity in advanced cervical cancer: a case report

Cervical cancer (CC) is the second most commonly diagnosed cancer and the third leading cause of cancer death among females. The options of treatment for recurrent/advanced CC are limited and patients experiencing recurrence after first line platinum-based chemotherapy have a poor prognosis. In this context, immune checkpoint inhibitors (ICI)s antagonizing PD-1 and programmed death-ligand 1 (PD-L1) have profoundly changed the treatment scenario and outcomes in CC in the first or subsequent lines both as monotherapies or in combination with chemotherapy or other ICIs. Herein, we report the clinical case of a 74-year-old woman with metastatic CC with negative tumor PD-L1 expression who having disease progression after first-line of systemic treatment with platinum, thus undergoing to anti-PD-1 namely cemiplimab. The patient achieved a surprising, fast and complete metabolic response to cemiplimab immediately discontinued after only two cycles due to the onset of rare and severe immune-related adverse events (irAE)s such cardiovascular toxicity and hypertransaminasemia. Despite this, thirteen months later, the patient remains disease-free despite cemiplimab was withdrawn.

Clinical utility of [18F]FDG PET/CT in the assessment of mediastinal lymph node disease after neoadjuvant chemoimmunotherapy for non-small cell lung cancer

OBJECTIVES

The performance of positron emission tomography/computed tomography (PET/CT) for the prediction of ypN2 disease in non-small cell lung cancer (NSCLC) after neoadjuvant chemoimmunotherapy has not been reported. This multicenter study investigated the utility of PET/CT to assess ypN2 disease in these patients.

METHODS

A total of 181 consecutive patients (chemoimmunotherapy = 86, chemotherapy = 95) at four institutions were enrolled in this study. Every patient received a PET/CT scan prior to surgery and complete resection with systematic nodal dissection. The diagnostic performance was evaluated through area under the curve (AUC). Kaplan-Meier method and Cox analysis were performed to identify the risk factors affecting recurrences.

RESULTS

The sensitivity, specificity, and accuracy of PET/CT for ypN2 diseases were 0.667, 0.835, and 0.779, respectively. Therefore, the AUC was 0.751. Compared with the false positive cases, the mean value of max standardized uptake value (SUVmax) (6.024 vs. 2.672, p < 0.001) of N2 nodes was significantly higher in true positive patients. Moreover, the SUVmax of true positive (7.671 vs. 5.976, p = 0.365) and false (2.433 vs. 2.339, p = 0.990) positive cases were similar between chemoimmunotherapy and chemotherapy, respectively. Survival analysis proved that pathologic N (ypN) 2 patients could be stratified by PET/CT-N2(+ vs. -) for both chemoimmunotherapy (p = 0.023) and chemotherapy (p = 0.010).

CONCLUSIONS

PET/CT is an accurate and non-invasive test for mediastinal restaging of NSCLC patients who receive neoadjuvant chemoimmunotherapy. The ypN2 patients with PET/CT-N2( +) are identified as an independent prognostic factor compared with PET/CT-N2(-).

CLINICAL RELEVANCE STATEMENT

Imaging with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) plays an integral role during disease diagnosis, staging, and therapeutic response assessments in patients with NSCLC. PET/CT could be an effective non-invasive tool for predicting ypN2 diseases after neoadjuvant chemoimmunotherapy.

KEY POINTS

• PET/CT could serve as an effective non-invasive tool for predicting ypN2 diseases. • The ypN2 patients with PET/CT-N2( +) were a strong and independent prognostic factor. • The application of PET/CT for restaging should be encouraged in clinical practice.

Visualization of microRNA therapy in cancers delivered by small extracellular vesicles

MicroRNA (miRNA) delivery by extracellular vesicles (EVs) has recently inspired tremendous developments in cancer treatments. However, hybridization between miRNA and its target mRNA is still difficult to be imaged in vivo to assess the therapeutic effects in time. Herein we design a nano-scale fluorescent "off-on" complex encapsulated by small extracellular vesicles (sEVs) for real-time visualization and evaluation of gene therapy efficiency in human gastric cancer cells and murine xenograft tumor models. The complex is formed by π-π stacking between graphene quantum dots (GQDs) and tumor suppressor miR-193a-3p conjugated fluorescent tag whose signals remain off when binding to GQDs. Loaded into sEVs using tunable sonication techniques, the GQDs/Cy5-miR particles enter the tumor cells and promote miR-193a-3p escape from endosomes. The miR-193a-3p in GQDs/Cy5-miR is unleashed to pair the specific target oncogene cyclin D1 (CCND1), therefore turning on the fluorescence of miRNA tags. We find out that GQDs/Cy5-miR@sEVs can activate the "turn-on" fluorescent signal and exhibit the longest retention time in vivo, which suggests a minimized degradation of miR-193a-3p in dynamic processes of miRNA-mRNA binding. More importantly, GQDs/Cy5-miR@sEVs significantly promote cancer apoptosis in vitro and in vivo via the enhanced cellular uptake. Our study demonstrates that GQDs/Cy5-miR@sEVs represent an efficient and refined theranostic platform for gene therapy in cancers.

The opportunities and challenges in immunotherapy: Insights from the regulation of PD-L1 in cancer cells

The immunosuppressive molecule programmed death-ligand 1 (PD-L1) is frequently upregulated in human cancers. Binding of PD-L1 to its receptor, programmed death-1 (PD-1), on activated T cells facilitates cancer cells to evade the host immune system. Antibody-based PD-1/PD-L1 inhibitors can inhibit PD-1/PD-L1 interaction allowing reactivate cytotoxic T cells to eradicate advanced cancer cells. However, the majority of cancer patients fail to respond to anti-PD-1/PD-L1 therapies and the molecular mechanisms for this remain poorly understood. Recent studies show that PD-L1 expression level on tumor cells affect the clinical efficacy of immune checkpoint therapies. Thus, furthering our understanding of the regulatory mechanisms of PD-L1 expression in cancer cells will be critical to improve clinical response rates and the efficacy of PD-1/PD-L1 immune therapies. Here we review recent studies, primarily focusing on the mechanisms that regulate PD-L1 expression at the transcriptional, post-transcriptional and protein level, with the purpose to drive the development of more targeted and effective anti-PD-1/PD-L1 cancer therapies.

Radionuclide-based theranostics - a promising strategy for lung cancer

PURPOSE

This review aims to provide a comprehensive overview of the latest literature on personalized lung cancer management using different ligands and radionuclide-based tumor-targeting agents.

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide. Due to the heterogeneity of lung cancer, advances in precision medicine may enhance the disease management landscape. More recently, theranostics using the same molecule labeled with two different radionuclides for imaging and treatment has emerged as a promising strategy for systemic cancer management. In radionuclide-based theranostics, the target, ligand, and radionuclide should all be carefully considered to achieve an accurate diagnosis and optimal therapeutic effects for lung cancer.

METHODS

We summarize the latest radiotracers and radioligand therapeutic agents used in diagnosing and treating lung cancer. In addition, we discuss the potential clinical applications and limitations associated with target-dependent radiotracers as well as therapeutic radionuclides. Finally, we provide our views on the perspectives for future development in this field.

CONCLUSIONS

Radionuclide-based theranostics show great potential in tailored medical care. We expect that this review can provide an understanding of the latest advances in radionuclide therapy for lung cancer and promote the application of radioligand theranostics in personalized medicine.

Positron emission tomography molecular imaging to monitor anti-tumor systemic response for immune checkpoint inhibitor therapy

Immune checkpoint inhibitors (ICIs) achieve a milestone in cancer treatment. Despite the great success of ICI, ICI therapy still faces a big challenge due to heterogeneity of tumor, and therapeutic response is complicated by possible immune-related adverse events (irAEs). Therefore, it is critical to assess the systemic immune response elicited by ICI therapy to guide subsequent treatment regimens. Positron emission tomography (PET) molecular imaging is an optimal approach in cancer diagnosis, treatment effect evaluation, follow-up, and prognosis prediction. PET imaging can monitor metabolic changes of immunocytes and specifically identify immuno-biomarkers to reflect systemic immune responses. Here, we briefly review the application of PET molecular imaging to date of systemic immune responses following ICI therapy and the associated rationale.

Imaging assessment of toxicity related to immune checkpoint inhibitors

In recent years, a wide range of cancer immunotherapies have been developed and have become increasingly important in cancer treatment across multiple oncologic diseases. In particular, immune checkpoint inhibitors (ICIs) offer promising options to improve patient outcomes. However, a major limitation of these treatments consists in the development of immune-related adverse events (irAEs) occurring in potentially any organ system and affecting up to 76% of the patients. The most frequent toxicities involve the skin, gastrointestinal tract, and endocrine system. Although mostly manageable, potentially life-threatening events, particularly due to neuro-, cardiac, and pulmonary toxicity, occur in up to 30% and 55% of the patients treated with ICI-monotherapy or -combination therapy, respectively. Imaging, in particular computed tomography (CT), magnetic resonance imaging (MRI), and 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT), plays an important role in the detection and characterization of these irAEs. In some patients, irAEs can even be detected on imaging before the onset of clinical symptoms. In this context, it is particularly important to distinguish irAEs from true disease progression and specific immunotherapy related response patterns, such as pseudoprogression. In addition, there are irAEs which might be easily confused with other pathologies such as infection or metastasis. However, many imaging findings, such as in immune-related pneumonitis, are nonspecific. Thus, accurate diagnosis may be delayed underling the importance for adequate imaging features characterization in the appropriate clinical setting in order to provide timely and efficient patient management. ¹⁸F-FDG-PET/CT and radiomics have demonstrated to reliably detect these toxicities and potentially have predictive value for identifying patients at risk of developing irAEs. The purpose of this article is to provide a review of the main immunotherapy-related toxicities and discuss their characteristics on imaging.

FDG-PET findings associated with various medical procedures and treatments

[¹⁸F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established modality with high sensitivity for the diagnosis and staging of oncologic patients. FDG is taken up by the glucose transporter of the cell membrane and becomes trapped within the cell. In addition to malignant neoplasms, active inflammatory lesions and some kinds of benign tumors also accumulate FDG. Moreover, the degree of uptake into normal organs and tissues depends on various physiological conditions, which is affected by various medical procedures, treatments, and drugs. To avoid misleading interpretations, it is important to recognize possible situations of unexpected abnormal accumulation that mimic tumor lesions. In this review, we present various FDG findings associated with surgical or medical procedures and treatments. Some findings reflect the expected physiological reaction to treatment, and some show inflammation due to prior procedures. Occasionally, FDG-PET visualizes other disorders that are unrelated to the malignancy, which may be associated with the adverse effects of certain drugs that the patient is taking. Careful review of medical records and detailed interviews of patients are thus necessary.

Tumor metabolic and secondary lymphoid organ metabolic markers on 18F-fludeoxyglucose positron emission tomography predict prognosis of immune checkpoint inhibitors in advanced lung cancer

Background

The purpose of this study was to investigate the predictive value of tumor metabolic parameters in combination with secondary lymphoid metabolic parameters on positron emission tomography (PET)/computed tomography (CT) for immune checkpoint inhibitor (ICI) prognosis in advanced lung cancer.

Methods

This study retrospectively included 125 patients who underwent 18F-fludeoxyglucose (FDG) PET/CT before ICI therapy, including 41 patients who underwent a second PET/CT scan during ICI treatment. The measured PET/CT parameters included tumor metabolism parameters [maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), total lesion glycolysis (TLG), and total metabolic tumor volume (TMTV)] and secondary lymphoid organ metabolism parameters [spleen-to-liver SUVmax ratio (SLR) and bone marrow-to-liver SUVmax ratio (BLR)]. The correlation of PET/CT metabolic parameters with early ICI treatment response, progression-free survival (PFS), and overall survival (OS) was analyzed.

Results

Within a median follow-up of 28.7 months, there were 44 responders and 81 non-responders. The median PFS was 8.6 months (95% confidence interval (CI): 5.872–11.328), and the median OS was 20.4 months (95% CI: 15.526–25.274). Pretreatment tumor metabolic parameters were not associated with early treatment responses. The high bone marrow metabolism (BLR &gt;1.03) was significantly associated with a shorter PFS (p = 0.008). Patients with a high TMTV (&gt;168 mL) and high spleen metabolism (SLR &gt;1.08) had poor OS (p = 0.019 and p = 0.018, respectively). Among the 41 patients who underwent a second PET/CT scan, the ΔSUVmax was significantly lower (p = 0.01) and the SLR was significantly higher (p = 0.0086) in the responders. Populations with low-risk characteristics (low TMTV, low SLR, and ΔSLR &gt; 0) had the longest survival times.

Conclusion

High pretreatment TMTV and SLR are associated with poor OS, and increased spleen metabolism after ICI therapy predicts treatment benefit. This indicates that the combination of tumor and spleen metabolic parameters is a valuable prognostic strategy.

Immune Checkpoint Inhibitors in Advanced NSCLC: [18F]FDG PET/CT as a Troubleshooter in Treatment Response

Introduction: The aim of this study was to investigate whether [¹⁸F]FDG PET/CT-derived semi-quantitative parameters can predict immunotherapy treatment response in non-small cell lung cancer (NSCLC) patients. Secondly, immune-related adverse events (irAEs) and lymphoid cell-rich organs activation were evaluated. Materials and Methods: Twenty-eight patients who underwent [¹⁸F]FDG PET/CT scans before and at first restaging therapy with immuno-checkpoint inhibitors (ICIs) were retrospectively analyzed. PET-based semi-quantitative parameters extracted from both scans were respectively: SUV_max and SUV_peak of the target lesion, whole-body metabolic tumor volume (MTV_WB), and whole-body total lesion glycolysis (TLG_WB), as well as their interval changes (ΔSUV_maxTL, ΔSUV_peakTL, ΔMTV_WB, ΔTLG_WB). These PET-derived parameters were correlated to controlled disease (CD) assessed by RECIST 1.1. IrAEs, if present, were also described and correlated with clinical benefit (CB). SUV_max of the spleen and bone marrow at restaging scans were also correlated to CB. Results: The CD was achieved in 54% of patients. Out of 28 eligible patients, 13 (46%) experienced progressive disease (PD), 7 showed SD, 7 had PR, and only in one patient CR was achieved. ΔSUV_maxTL (p = 0.002) and ΔSUV_peakTL (p < 0.001) as well as ΔMTV_WB (p < 0.001) and ΔTLG_WB (p < 0.005) were significantly associated with PD vs. non-PD. IrAEs and lymphoid cell-rich organs activation did not correlate with CB. Conclusions: [¹⁸F]FDG PET/CT by using interval changes of PET-derived semi-quantitative parameters could represent a reliable tool in immunotherapy treatment response evaluation in NSCLC patients.