Positron Emission Tomography for Response Evaluation in Microenvironment-Targeted Anti-Cancer Therapy

The role of baseline 18F-FDG PET/CT for survival prognosis in NSCLC patients undergoing immunotherapy: a systematic review and meta-analysis

Background

The value of pretreatment baseline 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/computed tomography (CT) as a prognostic factor for survival of patients with non-small-cell lung cancer (NSCLC) receiving immunotherapy remained uncertain.

Objectives

To investigate the prognostic ability of baseline 18F-FDG PET/CT in patients with NSCLC receiving immunotherapy.

Design

A systematic review and meta-analysis.

Data sources and methods

We searched the PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases until May 7, 2024, and extracted data related to patient characteristics, semiquantitative parameters of 18F-FDG PET/CT, and survival. We pooled hazard ratios (HRs) to evaluate the prognostic value of the maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for overall survival (OS) and progression-free survival (PFS).

Results

A total of 22 studies (1363 patients, average age range 30-88 years) were included. Baseline 18F-FDG PET/CT-derived MTV was significantly associated with both OS (HR: 1.124, 95% confidence interval (CI) 1.058-1.195, I 2 = 81.70%) and PFS (HR: 1.069, 95% CI: 1.016-1.124, I 2 = 71.80%). Other baseline 18F-FDG PET/CT-derived parameters, including SUVmax (OS: HR: 0.930, 95% CI: 0.718-1.230; PFS: HR: 0.979, 95% CI: 0.759-1.262), SUVmean (OS: HR: 0.801, 95% CI: 0.549-1.170; PFS: HR: 0.688, 95% CI: 0.464-1.020), and TLG (OS: HR: 0.999, 95% CI: 0.980-1.018; PFS: HR: 0.995, 95% CI: 0.980-1.010), were not associated with survival. Sensitivity analyses by removing one study at a time did not significantly alter the association between MTV and PFS or between MTV and OS. There was no evidence of publication bias.

Conclusion

Pretreatment baseline 18F-FDG PET/CT-derived MTV might be a prognostic biomarker in NSCLC patients receiving immunotherapy. Further studies are needed to support routine use.

The Utility of 18F-FDG-PET-CT Metabolic Parameters in Evaluating the Primary Tumor Aggressiveness and Lymph Node Metastasis of Nasopharyngeal Carcinoma

Background

Following changes in primary tumor (T) and lymph node (N) staging for nasopharyngeal carcinoma (NPC) in the Eighth Edition AJCC Cancer Staging Manual, simplification of T staging has been proposed. However, a limited range of 2-deoxy-2-[fluorine-18] fluoro-D-glucose positron emission tomography-computed tomography (18F-FDG PET-CT) metabolic parameters has been investigated. Therefore, we aimed to evaluate the primary tumor invasiveness and the lymph node metastasis (LNM) of NPC from a metabolic perspective.

Methods

A total of 435 NPC patients underwent 18F-FDG PET/CT before treatment were retrospectively examined. The primary endpoint was differences in standard uptake value (SUV), lean body mass-normalized SUV (SUL), body surface area-normalized SUV (SUS), glucose-normalized SUV (GN), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and glucose-normalized total lesion glycolysis (GNTLG) of primary tumors and LNM between different T and N stages. The metabolic parameters associated with T and N staging were identified.

Results

There were significant differences between all parameters relative to the primary tumor but no significant differences in any parameter relative to the LNM and T stages. Higher mean values of TGNmax, TGNmean, TSUVpeak, and TSUSmax were associated with advanced T stages. Higher mean values of all the LNM parameters were associated with more advanced N stages. Only primary tumor metabolic tumor volume (TMTV), TSUVpeak, TSULmax, and TSUSmax showed a significant positive association with T staging, while lymph node metabolic tumor volume (LNMTV) and TSUSmax were significantly positive in N staging.

Conclusions

Our findings suggest that metabolic parameters are useful indicators of tumor invasiveness and LNM based on the Eighth Edition manual. Compared with volume-dependent parameters, TGNmax, TGNmean, TSUVpeak, and TSUSmax may be better indicators of local tumor aggressiveness. SUSmax of the primary tumor was associated with LNM. In addition to SUVmax, other metabolic parameters (eg, SULmax, SUSmax, GNmax, and GNmean) could evaluate tumor aggressiveness and LNM better.

Analysis of Positive Results of 18F-FDG PET/CT Imaging after Hematopoietic Stem Cell Transplantation in Lymphoma

PURPOSE

The purpose of this study was to differentiate between false-positive and true-positive positron emission tomography (PET) results after hematopoietic stem cell transplantation (SCT) for lymphoma involvement by analyzing several clinical variables and specific imaging features.

PATIENTS AND METHODS

Patients with lymphoma who received SCT and underwent post-transplantation ¹⁸F-FDG PET/CT scans between January 2013 and April 2021 at our institution were included. Associations between PET positivity and related clinical information were assessed using t-tests and χ² tests. The significance of variables differentiating benign lesions from malignant FDG-avid lesions was evaluated by logistic regression analysis. Survival probabilities were derived from Kaplan-Meier curves and compared using the log-rank test.

RESULTS

A total of 185 patients (235 post-transplantation PET/CT scans) were enrolled in our present study. Compared with those with true-positive PET results, patients with false-positive PET results exhibited a better prognosis. For the autologous SCT group, false-positive cases were more commonly seen when FDG-avid foci appeared outside the sites of the original disease (p = 0.004), and the integrated CT imaging showed negative results (p = 0.000). In multivariate logistic regression analysis, integrated CT results were the only significant factor. For the allogeneic SCT group, false-positive cases were significantly more commonly seen when DS = 4 (p = 0.046), FDG-avid foci appeared outside the sites of the original disease (p = 0.022), and the integrated CT imaging showed negative results (p = 0.001). In a multivariate logistic regression analysis, whether FDG-avid foci were in the sites of the original disease and integrated CT results were both significant factors.

CONCLUSION

False-positive FDG uptake in post-transplantation PET was not uncommon. Several variables could provide an important reference to differentiate false-positive from true-positive post-SCT PET results for lymphoma involvement.

TRIAL REGISTRATION NUMBER

ChiCTR2300067355.

Integrating single-cell RNA-seq and spatial transcriptomics reveals MDK-NCL dependent immunosuppressive environment in endometrial carcinoma

Objectives

The tumor microenvironment (TME) play important roles in progression of endometrial carcinoma (EC). We aimed to assess the cell populations in TME of EC.

Methods

We downloaded datasets of single-cell RNA-seq (scRNA-seq) and spatial transcriptome (ST) for EC from GEO, and downloaded RNA-Seq (FPKM) and clinical data of TCGA-UCEC project from TCGA. The datasets were analyzed using R software.

Results

We obtained 5 datasets of scRNA-seq, 1 of ST and 569 samples of RNA-seq. Totally, 0.2 billion transcripts and 33,408 genes were detected in 33,162 cells from scRNA-seq. The cells were classified into 9 clusters, and EC cells were originated from epithelial cells and ciliated cells. Gene set variation analysis (GSVA) indicated that the pathways enriched in the subclusters of epithelial cells and endothelial cells were significantly different, indicating great heterogeneity in EC. Cell-cell communication analyses showed that EC cells emitted the strongest signals, and endothelial cells received more signals than other cells. Further analysis found that subclusters of 1 and 2 of epithelial cells were showed a more malignant phenotype, which may confer malignant phenotype to subcluster of 0 of endothelial cells through MK pathway by MDL-NCL signal. We also analyzed communications between spatial neighbors with ST data and confirmed the findings on MDL-NCL in cell-cell communication. TCGA and GEO analyses indicated that the expression levels of NCL was inversely correlated with ImmuneScore.

Conclusion

Our study revealed EC cells can confer malignant phenotype to endothelial cells by MDK-NCL signal, and NCL is associated with suppressed immune activity. EC cells may shape TME by inhibiting immune cells and “educating” stromal cells via MDK-NCL signal.

Cannot Target What Cannot Be Seen: Molecular Imaging of Cancer Stem Cells

Cancer stem cells are known to play a key role in tumour development, proliferation, and metastases. Their unique properties confer resistance to therapy, often leading to treatment failure. It is believed that research into the identification, targeting, and eradication of these cells can revolutionise oncological treatment. Based on the principle that what cannot be seen, cannot be targeted, a primary step in cancer management is the identification of these cells. The current review aims to encompass the state-of-the-art functional imaging techniques that enable the identification of cancer stem cells via various pathways and mechanisms. The paper presents in vivo molecular techniques that are currently available or await clinical implementation. Challenges and future prospects are highlighted to open new research avenues in cancer stem cell imaging.

Tumour microenvironment in pheochromocytoma and paraganglioma

Pheochromocytomas and Paragangliomas (Pheo/PGL) are rare catecholamine-producing tumours derived from adrenal medulla or from the extra-adrenal paraganglia respectively. Around 10-15% of Pheo/PGL develop metastatic forms and have a poor prognosis with a 37% of mortality rate at 5 years. These tumours have a strong genetic determinism, and the presence of succinate dehydrogenase B (SDHB) mutations are highly associated with metastatic forms. To date, no effective treatment is present for metastatic forms. In addition to cancer cells, the tumour microenvironment (TME) is also composed of non-neoplastic cells and non-cellular components, which are essential for tumour initiation and progression in multiple cancers, including Pheo/PGL. This review, for the first time, provides an overview of the roles of TME cells such as cancer-associated fibroblasts (CAFs) and tumour-associated macrophages (TAMs) on Pheo/PGL growth and progression. Moreover, the functions of the non-cellular components of the TME, among which the most representatives are growth factors, extracellular vesicles and extracellular matrix (ECM) are explored. The importance of succinate as an oncometabolite is emerging and since Pheo/PGL SDH mutated accumulate high levels of succinate, the role of succinate and of its receptor (SUCNR1) in the modulation of the carcinogenesis process is also analysed. Further understanding of the mechanism behind the complicated effects of TME on Pheo/PGL growth and spread could suggest novel therapeutic targets for further clinical treatments.

Cysteine-specific 89Zr-labeled anti-CD25 IgG allows immuno-PET imaging of interleukin-2 receptor-α on T cell lymphomas

Introduction

Positron emission tomography (PET) using radiolabeled Abs as imaging tracer is called immuno-PET. Immuno-PET can verify therapeutic Ab delivery and can noninvasively quantify global levels of target expression in tumors of living subjects. The interleukin-2 receptor α chain (IL-2Rα; CD25) is a promising target for immune therapy and radioimmunotherapy of lymphomas. Immuno-PET could facilitate this approach by visualizing CD25 expression in vivo.

Methods

We prepared ⁸⁹Zr-anti-CD25 IgG specifically labeled to sulfhydryl moieties by maleimide-deferoxamine conjugation.

Results and Discussion

CD25(+) SUDHL1 human T-cell lymphoma cells showed high anti-human ⁸⁹Zr-CD25 IgG binding that reached 32-fold of that of CD25(-) human lymphoma cells and was completely blocked by excess unlabeled Ab. In SUDHL1 tumor-bearing nude mice, pharmacokinetic studies demonstrated exponential reductions of whole blood and plasma activity following intravenous ⁸⁹Zr-anti-CD25 IgG injection, with half-lives of 26.0 and 23.3 h, respectively. SUDHL1 tumor uptake of ⁸⁹Zr-CD25 IgG was lower per weight in larger tumors, but blood activity did not correlate with tumor size or blood level of human CD25, indicating minimal influence by circulating soluble CD25 protein secreted from the lymphoma cells. ⁸⁹Zr-CD25 IgG PET allowed high-contrast SUDHL1 lymphoma visualization at five days. Biodistribution studies confirmed high tumor ⁸⁹Zr-CD25 IgG uptake (8.7 ± 0.9%ID/g) that was greater than blood (5.2 ± 1.6%ID/g) and organ uptakes (0.7 to 3.5%ID/g). Tumor CD25-specific targeting was confirmed by suppression of tumor uptake to 4.3 ± 0.2%ID by excess unlabeled CD25 IgG, as well as by low tumor uptake of ⁸⁹Zr-labeled IgG2a isotype control Ab (3.6 ± 0.9%ID). Unlike CD25(+) lymphocytes from mouse thymus that showed specific uptake of anti-mouse ⁸⁹Zr-CD25 IgG, EL4 mouse lymphoma cells had low CD25 expression and showed low uptake. In immunocompetent mice bearing EL4 tumors, anti-mouse ⁸⁹Zr-CD25 IgG displayed low uptakes in normal organs as well as in the tumor. Furthermore, the biodistribution was not influenced by Ab blocking, indicating that specific uptake in nontumor tissues was minimal. ⁸⁹Zr-CD25 IgG immuno-PET may thus be useful for imaging of T-cell lymphomas and noninvasive assessment of CD25 expression on target cells in vivo.

Monitoring of Current Cancer Therapy by Positron Emission Tomography and Possible Role of Radiomics Assessment

Evaluation of cancer therapy with imaging is crucial as a surrogate marker of effectiveness and survival. The unique response patterns to therapy with immune-checkpoint inhibitors have facilitated the revision of response evaluation criteria using FDG-PET, because the immune response recalls reactive cells such as activated T-cells and macrophages, which show increased glucose metabolism and apparent progression on morphological imaging. Cellular metabolism and function are critical determinants of the viability of active cells in the tumor microenvironment, which would be novel targets of therapies, such as tumor immunity, metabolism, and genetic mutation. Considering tumor heterogeneity and variation in therapy response specific to the mechanisms of therapy, appropriate response evaluation is required. Radiomics approaches, which combine objective image features with a machine learning algorithm as well as pathologic and genetic data, have remarkably progressed over the past decade, and PET radiomics has increased quality and reliability based on the prosperous publications and standardization initiatives. PET and multimodal imaging will play a definitive role in personalized therapeutic strategies by the precise monitoring in future cancer therapy.

Tumor endothelial cell-derived extracellular vesicles contribute to tumor microenvironment remodeling

Cancer progression involves several biological steps where angiogenesis is a key tumorigenic phenomenon. Extracellular vesicles (EVs) derived from tumor cells and other cells in the tumor microenvironment (TME) help modulate and maintain favorable microenvironments for tumors. Endothelial cells (ECs) activated by cancer-derived EVs have important roles in tumor angiogenesis. Interestingly, EVs from ECs activate tumor cells, i.e. extracellular matrix (ECM) remodeling and provide more supplements for tumor cells. Thus, EV communications between cancer cells and ECs may be effective therapeutic targets for controlling cancer progression. In this review, we describe the current knowledge on EVs derived from ECs and we examine how these EVs affect TME remodeling.

Interest and Limits of [18F]ML-10 PET Imaging for Early Detection of Response to Conventional Chemotherapy

One of the current challenges in oncology is to develop imaging tools to early detect the response to conventional chemotherapy and adjust treatment strategies when necessary. Several studies evaluating PET imaging with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) as a predictive tool of therapeutic response highlighted its insufficient specificity and sensitivity. The [¹⁸F]FDG uptake reflects only tumor metabolic activity and not treatment-induced cell death, which seems to be relevant for therapeutic evaluation. Therefore, to evaluate this parameter in vivo, several cell death radiotracers have been developed in the last years. However, few of them have reached the clinical trials. This systematic review focuses on the use of [¹⁸F]ML-10 (2-(5-[¹⁸F]fluoropentyl)-2-methylmalonic acid) as radiotracer of apoptosis and especially as a measure of tumor response to treatment. A comprehensive literature review concerning the preclinical and clinical investigations conducted with [¹⁸F]ML-10 was performed. The abilities and applications of this radiotracer as well as its clinical relevance and limitations were discussed. Most studies highlighted a good ability of the radiotracer to target apoptotic cells. However, the increase in apoptosis during treatment did not correlate with the radiotracer tumoral uptake, even using more advanced image analysis (voxel-based analysis). [¹⁸F]ML-10 PET imaging does not meet current clinical expectations for early detection of the therapeutic response to conventional chemotherapy. This review has pointed out the challenges of applying various apoptosis imaging strategies in clinical trials, the current methodologies available for image analysis and the future of molecular imaging to assess this therapeutic response.