Correlations between circulating tumor cell phenotyping and 18F-fluorodeoxyglucose positron emission tomography uptake in non-small cell lung cancer

Research progress on the multi-omics and survival status of circulating tumor cells

In the dynamic process of metastasis, circulating tumor cells (CTCs) emanate from the primary solid tumor and subsequently acquire the capacity to disengage from the basement membrane, facilitating their infiltration into the vascular system via the interstitial tissue. Given the pivotal role of CTCs in the intricate hematogenous metastasis, they have emerged as an essential resource for a deeper comprehension of cancer metastasis while also serving as a cornerstone for the development of new indicators for early cancer screening and new therapeutic targets. In the epoch of precision medicine, as CTC enrichment and separation technologies continually advance and reach full fruition, the domain of CTC research has transcended the mere straightforward detection and quantification. The rapid advancement of CTC analysis platforms has presented a compelling opportunity for in-depth exploration of CTCs within the bloodstream. Here, we provide an overview of the current status and research significance of multi-omics studies on CTCs, including genomics, transcriptomics, proteomics, and metabolomics. These studies have contributed to uncovering the unique heterogeneity of CTCs and identifying potential metastatic targets as well as specific recognition sites. We also review the impact of various states of CTCs in the bloodstream on their metastatic potential, such as clustered CTCs, interactions with other blood components, and the phenotypic states of CTCs after undergoing epithelial-mesenchymal transition (EMT). Within this context, we also discuss the therapeutic implications and potential of CTCs.

Advances in liquid biopsy-based markers in NSCLC

Lung cancer is the second most-frequently occurring cancer and the leading cause of cancer-associated deaths worldwide. Non-small cell lung cancer (NSCLC), the most common type of lung cancer is often diagnosed in middle or advanced stages and have poor prognosis. Diagnosis of disease at an early stage is a key factor for improving prognosis and reducing mortality, whereas, the currently used diagnostic tools are not sufficiently sensitive for early-stage NSCLC. The emergence of liquid biopsy has ushered in a new era of diagnosis and management of cancers, including NSCLC, since analysis of circulating tumor-derived components, such as cell-free DNA (cfDNA), circulating tumor cells (CTCs), cell-free RNAs (cfRNAs), exosomes, tumor-educated platelets (TEPs), proteins, and metabolites in blood or other biofluids can enable early cancer detection, treatment selection, therapy monitoring and prognosis assessment. There have been great advances in liquid biopsy of NSCLC in the past few years. Hence, this chapter introduces the latest advances on the clinical application of cfDNA, CTCs, cfRNAs and exosomes, with a particular focus on their application as early markers in the diagnosis, treatment and prognosis of NSCLC.

Circulating tumor cells: biology and clinical significance

Circulating tumor cells (CTCs) are tumor cells that have sloughed off the primary tumor and extravasate into and circulate in the blood. Understanding of the metastatic cascade of CTCs has tremendous potential for the identification of targets against cancer metastasis. Detecting these very rare CTCs among the massive blood cells is challenging. However, emerging technologies for CTCs detection have profoundly contributed to deepening investigation into the biology of CTCs and have facilitated their clinical application. Current technologies for the detection of CTCs are summarized herein, together with their advantages and disadvantages. The detection of CTCs is usually dependent on molecular markers, with the epithelial cell adhesion molecule being the most widely used, although molecular markers vary between different types of cancer. Properties associated with epithelial-to-mesenchymal transition and stemness have been identified in CTCs, indicating their increased metastatic capacity. Only a small proportion of CTCs can survive and eventually initiate metastases, suggesting that an interaction and modulation between CTCs and the hostile blood microenvironment is essential for CTC metastasis. Single-cell sequencing of CTCs has been extensively investigated, and has enabled researchers to reveal the genome and transcriptome of CTCs. Herein, we also review the clinical applications of CTCs, especially for monitoring response to cancer treatment and in evaluating prognosis. Hence, CTCs have and will continue to contribute to providing significant insights into metastatic processes and will open new avenues for useful clinical applications.

FDG-PET predicts bone invasion and prognosis in patients with oral squamous cell carcinoma

¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) is widely used for tumor staging. This study sought to determine the relationship of preoperative primary tumor SUVmax (tSUVmax) with the clinicopathological features of patients with OSCC and to compare the prognostic ability of tSUVmax with that of other recurrence factors. Data of 340 patients with OSCC who were diagnosed, treated, and followed up at the Changhua Christian Hospital were retrospectively analyzed. Only patients with OSCC arising from gingiva, palate, floor of the mouth, and retromolar trigone and those who had received preoperative FDG-PET within 2 weeks before surgery were included. tSUVmax value > 9.2 was the strong predictor of bone invasion (area under the receiver operating characteristic curve, 0.844). tSUVmax value > 7.2 showed a strong association with advanced pathological T stage and recurrence factors and was associated with poor survival; tSUVmax > 7.2 showed stronger predictive power for poor disease-free survival (DFS) than pT stage and the other recurrence factors related to primary tumor. FDG-PET can be a useful supplement to contrast-enhanced computed tomography or contrast-enhanced magnetic resonance imaging for diagnosing bone invasion by OSCC. The tSUVmax value was an independent predictor of DFS in this study.

Clinical Relevance of Mesenchymal- and Stem-Associated Phenotypes in Circulating Tumor Cells Isolated from Lung Cancer Patients

Simple Summary

Lung cancer is the most frequent malignancy in the world. Most lung cancer patients are diagnosed at an advanced stage. To make matters worse, the survival of patients is very poor. Circulating tumor cells (CTCs), albeit rare, have been portrayed as essential players in the progression of lung cancer. It is definitely not easy being a CTC. First, they escape from the primary tumor, then they travel in the bloodstream, have to survive really harsh conditions, and finally, they form metastases. The adoption of epithelial-to-mesenchymal transition as well as cancer stem cell features has been suggested to allow CTCs to survive and metastasize. This review will focus on how these features can be used to estimate the prognosis of lung cancer patients.

Abstract

Lung cancer is the leading cause of cancer-related mortality globally. Among the types of lung cancer, non-small-cell lung cancer (NSCLC) is more common, while small-cell lung cancer (SCLC) is less frequent yet more aggressive. Circulating tumor cells (CTCs), albeit rare, have been portrayed as essential players in the progression of lung cancer. CTCs are considered to adopt an epithelial-to-mesenchymal transition (EMT) phenotype and characteristics of cancer stem cells (CSCs). This EMT (or partial) phenotype affords these cells the ability to escape from the primary tumor, travel into the bloodstream, and survive extremely adverse conditions, before colonizing distant foci. Acquisition of CSC features, such as self-renewal, differentiation, and migratory potential, further reflect CTCs’ invasive potential. CSCs have been identified in lung cancer, and expression of EMT markers has previously been correlated with poor clinical outcomes. Thus far, a vast majority of studies have concentrated on CTC detection and enumeration as a prognostic tools of patients’ survival or for monitoring treatment efficacy. In this review, we highlight EMT and CSC markers in CTCs and focus on the clinical significance of these phenotypes in the progression of both non-small- and small-cell lung cancer.

18F-FDG PET/CT and circulating tumor cells in treatment-naive patients with non-small-cell lung cancer

PURPOSE

This study retrospectively investigated the clinical utility of 2-deoxy-18F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and circulating tumor cells (CTCs) in the diagnosis and prognosis of treatment-naive patients with non-small-cell lung cancer (NSCLC).

METHODS

The blood samples of treatment-naive patients with NSCLC were collected for CTCs detection, and the tumor metabolic parameters of ¹⁸F-FDG PET/CT, including maximum standard uptake value (SUVmax), metabolic tumor volume of primary lesion (MTV-P) and combination of primary lesion and metastases (MTV-C), and total lesion glycolysis of primary lesion (TLG-P) and combination of primary lesion and metastases (TLG-C), were analyzed. Age, sex, smoking, serum tumor markers, tumor size, location, TNM stage, and genetic mutations were also reviewed. Moreover, progression-free survival (PFS) and overall survival (OS) of these patients were analyzed.

RESULTS

A total of 309 patients with NSCLC (200 men, 109 women; mean age: 61 ± 9 years) were enrolled in this study, including 217 patients with adenocarcinoma and 92 with squamous cell carcinoma. Of the 309 cases, 11 were misdiagnosed with benign diseases by ¹⁸F-FDG PET/CT. CTCs positivity was detected in 234 cases. The sensitivity of ¹⁸F-FDG PET/CT and CTCs in NSCLC were 96.4% and 75.7%, respectively. SUVmax, MTV-P, TLG-P, MTV-C, TLG-C, tumor size, and serum CYFRA211 levels were significantly higher in CTCs positive group than negative group; and advanced TNM stage, squamous cell carcinoma, and EGFR wild type presented higher CTCs positivity. Multivariate logistic regression analysis revealed that SUVmax was significantly associated with CTCs positivity. Multivariate cox regression analysis showed that TLG-P, TLG-C, and CTCs were independent predictors of PFS in patients with NSCLC, and TLG-C and CTCs were independent predictors of OS.

CONCLUSIONS

¹⁸F-FDG PET/CT was superior to CTCs in the diagnosis of treatment-naive patients with NSCLC. The levels of CTCs in the peripheral blood were associated with tumor glucose metabolism in NSCLC. Metabolic parameters of ¹⁸F-FDG PET/CT and CTCs could separately predict the outcomes of treatment-naive patients with NSCLC.