Overcoming Obstacles in Pathological Diagnosis of Pulmonary Nodules through Circulating Tumor Cell Enrichment

Current advances and future prospects of blood-based techniques for identifying benign and malignant pulmonary nodules

Lung cancer is the leading cause of cancer-related mortality worldwide, highlighting the urgent need for more accurate and minimally invasive diagnostic tools to improve early detection and patient outcomes. While low-dose computed tomography (LDCT) is effective for screening in high-risk individuals, its high false-positive rate necessitates more precise diagnostic strategies. Liquid biopsy, particularly ctDNA methylation analysis, represents a promising alternative for non-invasive classification of indeterminate pulmonary nodules (IPNs). This review highlights the progress and clinical potential of liquid biopsy technologies, including traditional proteins markers, cfDNA, exosomes, metabolomics, circulating tumor cells (CTCs) and platelets, in lung cancer diagnosis. We discuss the integration of ctDNA methylation analysis with traditional imaging and clinical data to enhance the early detection of IPNs, as well as potential solutions to address the challenges of low biomarker concentration and background noise. By advancing precision diagnostics, liquid biopsy technologies could transform lung cancer management, improve survival rates, and reduce the disease burden.

Minimally invasive biomarkers for triaging lung nodules-challenges and future perspectives

CT chest scans are commonly performed worldwide, either in routine clinical practice for a wide range of indications or as part of lung cancer screening programs. Many of these scans detect lung nodules, which are small, rounded opacities measuring 8-30 mm. While the concern about nodules is that they may represent early lung cancer, in screening programs, only 1% of such nodules turn out to be cancer. This leads to a series of complex decisions and, at times, unnecessary biopsies for nodules that are ultimately determined to be benign. Additionally, patients may be anxious about the status of detected lung nodules. The high rate of false positive lung nodule detections has driven advancements in biomarker-based research aimed at triaging lung nodules (benign versus malignant) to identify truly malignant nodules better. Biomarkers found in biofluids and breath hold promise owing to their minimally invasive sampling methods, ease of use, and cost-effectiveness. Although several biomarkers have demonstrated clinical utility, their sensitivity and specificity are still relatively low. Combining multiple biomarkers could enhance the characterisation of small pulmonary nodules by addressing the limitations of individual biomarkers. This approach may help reduce unnecessary invasive procedures and accelerate diagnosis in the future. This review offers a thorough overview of emerging minimally invasive biomarkers for triaging lung nodules, emphasising key challenges and proposing potential solutions for biomarker-based nodule differentiation. It focuses on diagnosis rather than screening, analysing research published primarily in the past five years with some exceptions. The incorporation of biomarkers into clinical practice will facilitate the early detection of malignant nodules, leading to timely interventions and improved outcomes. Further efforts are needed to increase the cost-effectiveness and practicality of many of these applications in clinical settings. However, the range of technologies is advancing rapidly, and they may soon be implemented in clinics in the near future.

The culture and application of circulating tumor cell-derived organoids

Circulating tumor cells (CTCs), which have the heterogeneity and histological properties of the primary tumor and metastases, are shed from the primary tumor and/or metastatic lesions into the vasculature and initiate metastases at remote sites. In the clinic, CTCs are used extensively in liquid biopsies for early screening, diagnosis, treatment, and prognosis. Current research focuses on using CTC-derived models to study tumor heterogeneity and metastasis, with 3D organoids emerging as a promising tool in cancer research and precision oncology. However, isolating and enriching CTCs from blood remains challenging due to their scarcity, exacerbated by the lack of an optimized culture medium for CTC-derived organoids (CTCDOs). In this review, we summarize the origin, isolation, enrichment, culture, validation, and clinical application of CTCs and CTCDOs.

Enumeration and Molecular Characterization of Circulating Tumor Cell Using an Epithelial Cell Adhesion Molecule/Vimentin/Epidermal Growth Factor Receptor Joint Capture System in Lung Cancer

Background

Detection rate and isolation yield of circulating tumor cells (CTCs) are low in lung cancer with approaches due to CTC invasiveness and heterogeneity. In this study, on the basis of the epithelial cell adhesion molecule (EpCAM) phenotype, markers of vimentin and epidermal growth factor receptor (EGFR) phenotype were added to jointly construct a precise and efficient CTC capture system for capture of lung cancer CTCs.

Methods

A CTC capture system combined with EpCAM lipid magnetic bead (Ep-LMB)/vimentin lipid magnetic bead (Vi-LMB)/EGFR lipid magnetic bead (EG-LMB) was constructed, and its performance was tested. The amount of CTC captured in the blood of patients with lung cancer was detected by immunofluorescence identification and analyzed for clinical relevance.

Results

The constructed CTC capture system has low cytotoxicity. The capture efficiency of lung cancer cells in phosphate belanced solution (PBS) system was 95.48%. The capture efficiency in the blood simulation system is 94.55%. The average number of CTCs in the blood of patients with lung cancer was 9.73/2 mL. The quantity distribution of CTCs is significantly correlated with tumor staging and metastasis. The area under the curve (AUC) of CTCs for the diagnosis of lung cancer was 0.9994 (95% CI = 0.9981-1.000, P < .0001). The cutoff value was 4.5/2 mL. The sensitivity was 99.39%, and the specificity was 96.88%.

Conclusion

The EpCAM/vimentin/EGFR combined capture system has feasibility and high sensitivity in the detection of lung cancer CTC typing, which can be used as an auxiliary diagnostic indicator for lung cancer and is expected to promote the clinical application of CTCs.

Identify the Clinicopathological Characteristics of Lung Carcinoma Patients Being False Negative in Folate Receptor Based Circulating Tumor Cell Detection

In lung cancer diagnosis, folate receptor (FR)-based circulating tumor cell (CTC) has shown its ability to distinguish malignancy from benign disease to some extent. However, there are still some patients that cannot be identified by FR-based CTC detection. And studies comparing the characteristics between true positive (TP) and false negative (FN) patients are few. Thus, the study comprehensively analyzes the clinicopathological characteristics of FN and TP patients in the current study. According to inclusion and exclusion criteria, 3420 patients are enrolled. Combining the pathological diagnosis with CTC results, patients are divided into FN and TP groups, and clinicopathological characteristics are compared between two groups. Compared with TP patients, FN patients have smaller tumor, early T stage, early pathological stage, and without lymph node metastasis. Epidermal growth factor receptor (EGFR) mutation status is different between FN and TP group. And this result is also demonstrated in lung adenocarcinoma subgroup but not in lung squamous cell carcinoma subgroup. Tumor size, T stage, pathological stage, lymph node metastasis, and EGFR mutation status may influence the accuracy of FR-based CTC detection in lung cancer. However, further prospective studies are needed to confirm the findings.

A combined diagnostic model based on circulating tumor cell in patients with solitary pulmonary nodules

BACKGROUND

Although many prediction models in diagnosis of solitary pulmonary nodules (SPNs) have been developed, few are widely used in clinical practice. It is therefore imperative to identify novel biomarkers and prediction models supporting early diagnosis of SPNs. This study combined folate receptor-positive circulating tumor cells (FR+ CTC) with serum tumor biomarkers, patient demographics and clinical characteristics to develop a prediction model.

METHODS

A total of 898 patients with a solitary pulmonary nodule who received FR+ CTC detection were randomly assigned to a training set and a validation set in a 2:1 ratio. Multivariate logistic regression was used to establish a diagnostic model to differentiate malignant and benign nodules. The receiver operating curve (ROC) and the area under the curve (AUC) were calculated to assess the diagnostic efficiency of the model.

RESULTS

The positive rate of FR+ CTC between patients with non-small cell lung cancer (NSCLC) and benign lung disease was significantly different in both the training and the validation dataset (p < 0.001). The FR+ CTC level was significantly higher in the NSCLC group compared with that of the benign group (p < 0.001). FR+ CTC (odds ratio, OR, 95% confidence interval, CI: 1.13, 1.07-1.19, p < 0.0001), age (OR, 95% CI: 1.06, 1.01-1.12, p = 0.03) and sex (OR, 95% CI: 1.07, 1.01-1.13, p = 0.01) were independent risk factors of NSCLC in patients with a solitary pulmonary nodule. The area under the curve (AUC) of FR+ CTC in diagnosing NSCLC was 0.650 (95% CI, 0.587-0.713) in the training set and 0.700 (95% CI, 0.603-0.796) in the validation set, respectively. The AUC of the combined model was 0.725 (95% CI, 0.659-0.791) in the training set and 0.828 (95% CI, 0.754-0.902) in the validation set, respectively.

CONCLUSIONS

We confirmed the value of FR+ CTC in diagnosing SPNs and developed a prediction model based on FR+ CTC, demographic characteristics, and serum biomarkers for differential diagnosis of solitary pulmonary nodules.

Single-Cell Enzymatic Screening for Epithelial Mesenchymal Transition with an Ultrasensitive Superwetting Droplet-Array Microchip

The phenotypic changes of circulating tumor cells (CTCs) during the epithelial-mesenchymal transition (EMT) have been a hot topic in tumor biology and cancer therapeutic development. Here, an integrated platform of single-cell fluorescent enzymatic assays with superwetting droplet-array microchips (SDAM) for ultrasensitive functional screening of epithelial-mesenchymal sub-phenotypes of CTCs is reported. The SDAM can generate high-density, volume well-defined droplet (0.66 nL per droplet) arrays isolating single tumor cells via a discontinuous dewetting effect. It enables sensitive detection of MMP9 enzyme activities secreted by single tumor cells, correlating to their epithelial-mesenchymal sub-phenotypes. In the pilot clinical double-blind tests, the authors have demonstrated that SDAM assays allow for rapid identification and functional screening of CTCs with different epithelial-mesenchymal properties. The consistency with the clinical outcomes validates the usefulness of single-cell secreted MMP9 as a biomarker for selective CTC screening and tumor metastasis monitoring. Convenient addressing and recovery of individual CTCs from SDAM have been demonstrated for gene mutation sequencing, immunostaining, and transcriptome analysis, revealing new understandings of the signaling pathways between MMP9 secretion and the EMT regulation of CTCs. The SDAM approach combined with sequencing technologies promises to explore the dynamic EMT plasticity of tumors at the single-cell level.

The value of folate receptor-positive circulating tumor cells in the diagnosis of lung cancer and its correlation with clinical characteristics

OBJECTIVE

The aim of this research is to investigate the feasibility of folate receptor-positive circulating tumor cells (FR+CTCs) as a biomarker for the diagnosis of malignant pulmonary nodules and the correlation between clinicopathological factors and FR+CTC levels.

METHODS

Patients initially diagnosed with one or more pulmonary nodules from a computed tomography scan were prospectively included. Three milliliters of peripheral blood was collected from each participant for FR+CTC analysis prior to surgery. Clinical and pathological parameters and FR+CTC levels were compared between patients with lung cancer and benign diseases.

RESULTS

Six hundred fifty-three patients had lung cancer and the other 124 had benign lung diseases based on pathological examinations of the resected specimens. The median FR+CTC value of the lung cancer group was 12.0 (95% CI 9.6-16.2) FU/3 mL and that of the benign group was 7.2 (95% CI 5.78-11.2) FU/3 mL. The difference was statistically significant (P < 0.0001). In a receiver operating characteristic analysis to distinguish the two groups, the area under curve of FR+CTC was 0.7457 (95% CI 0.6893-0.8021; P < 0.0001) using a cutoff of 8.65 FU/3 mL. The sensitivity was 86.37%, and the specificity was 74.19%. Combined with conventional serum tumor biomarkers, the area under curve was 0.922 (0.499-0.963). The sensitivity was 92.20%, and the specificity was 83.05%. FR+CTC levels were related to tumor staging (P4 < 0.001), the degree of tumor invasion both in single (P = 0.011) and multiple lesions (P = 0.022), pathological subtypes (P = 0.013), and maximum tumor diameter (P = 0.014).

CONCLUSIONS

FR+CTC is an effective and reliable biomarker for the diagnosis of lung cancer. Further, FR+CTC level is correlated with tumor staging, degree of invasion, pathological subtypes, and tumor size.

Preoperative levels of folate receptor-positive circulating tumor cells in different subtypes of early-stage lung adenocarcinoma: Predictive value for determining extent of surgical resection

Background

The objective was to measure the correlations of preoperative levels of folate receptor-positive circulating tumor cells (FR⁺CTCs) with clinical characteristics and histologic subtype in early-stage lung adenocarcinoma, and to determine the predictive value of FR⁺CTC level in preoperative determination of the extent of surgical resection.

Patients and methods

In this retrospective, single-institution, observational study, preoperative FR⁺CTC levels were measured via ligand-targeted enzyme-linked polymerization in patients with early-stage lung adenocarcinoma. Receiver operating characteristic (ROC) analysis was used to identify the optimal cutoff value of FR⁺CTC level for prediction of various clinical characteristics and histologic subtypes.

Results

No significant difference in FR⁺CTC level was observed among patients with adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma (IAC) (P = 0.813). Within the non-mucinous adenocarcinoma group, no difference was observed among patients with tumors whose predominant growth patterns were lepidic, acinar, papillary, micropapillary, solid, and complex gland (P = 0.053). However, significant differences in FR⁺CTC level were observed between patients with and without the micropapillary subtype [11.21 (8.22-13.61) vs. 9.85 (7.43-12.63), P = 0.017], between those with and without the solid subtype [12.16 (8.27-14.90) vs. 9.87 (7.50-12.49), P = 0.022], and between those with any of the advanced subtypes (micropapillary, solid, or complex glands) vs. none of these [10.48 (7.83-13.67) vs. 9.76 (7.42-12.42), P = 0.032]. FR⁺CTC level was also correlated with degree of differentiation of lung adenocarcinoma (P = 0.033), presence of visceral pleural invasion (VPI) of lung carcinoma (P = 0.003), and lymph node metastasis of lung carcinoma (P = 0.035).

Conclusion

FR⁺CTC level is of potential predictive value in determining the presence of aggressive histologic patterns (micropapillary, solid, and advanced subtypes), degree of differentiation, and occurrence of VPI and lymph node metastasis in IAC. Measurement of FR⁺CTC level combined with intraoperative frozen sections may represent a more effective method of guiding resection strategy in cases of cT1N0M0 IAC with high-risk factors.

The combination of computed tomography features and circulating tumor cells increases the surgical prediction of visceral pleural invasion in clinical T1N0M0 lung adenocarcinoma

Background

Visceral pleural invasion (VPI) is a clinical manifestation associated with a poor prognosis, and diagnosing it preoperatively is highly imperative for successful sublobar resection of these peripheral tumors. We evaluated the roles of computed tomography (CT) features and circulating tumor cells (CTCs) for improving VPI detection in patients with clinical T1N0M0 invasive lung adenocarcinoma.

Methods

Three hundred and ninety-one patients were reviewed retrospectively in this study, of which 234 presented with a pleural tag or pleural contact on CT images. CTCs positive for the foliate receptors were enriched and analyzed prior to surgery. Logistic regression analyses were performed to assess the association of CT features and CTCs with VPI, and the receiver operating characteristic (ROC) curve was generated to compare the predictive power of these variables.

Results

Patients mostly underwent either segmentectomies (18.9%) or lobectomies (79.0%). Only 49 of the 234 patients with pleural involvement on CT showed pathologically confirmed VPI. Multivariate logistic regression analysis revealed that CTC level ≥10.42 FU/3 mL was a significant VPI risk factor for invasive adenocarcinoma cases ≤30 mm [adjusted odds ratio (OR) =4.62, 95% confidence interval (CI): 2.05–10.44, P<0.001]. Based on CT features, subgroup analyses showed that the solid portion size was a statistically significant independent predictor of VPI for these peripheral nodules with pleural tag, while the solid portion length of the interface was an independent predictor of pleural contact. The receiver operating curve analyses showed that the combination of CTC and CT features were highly predictive of VPI [area under the curve (AUC) =0.921 for pleural contact and 0.862 for the pleural tag, respectively].

Conclusions

CTC, combined with CT features of pleural tag or pleural contact, could significantly improve VPI detection in invasive lung adenocarcinomas at clinical T1N0M0 stage prior to the patient’s surgery.

Blood-based liquid biopsy: Insights into early detection and clinical management of lung cancer

Currently, early detection of lung cancer relies on the characterisation of images generated from computed tomography (CT). However, lung tissue biopsy, a highly invasive surgical procedure, is required to confirm CT-derived diagnostic results with very high false-positive rates. Hence, a non-invasive or minimally invasive biomarkers is essential to complement the existing low-dose CT (LDCT) for early detection, improve responses to a certain treatment, predict cancer recurrence, and to evaluate prognosis. In the past decade, liquid biopsies (e.g., blood) have been demonstrated to be highly effective for lung cancer biomarker discovery. In this review, the roles of emerging liquid biopsy-derived biomarkers such as circulating nucleic acids, circulating tumour cells (CTCs), long non-coding RNA (lncRNA), and microRNA (miRNA), as well as exosomes, have been highlighted. The advantages and limitations of these blood-based minimally invasive biomarkers have been discussed. Furthermore, the current progress of the identified biomarkers for clinical management of lung cancer has been summarised. Finally, a potential strategy for the early detection of lung cancer, using a combination of LDCT scans and well-validated biomarkers, has been discussed.

Detection and clinical significance of circulating tumor cells in colorectal cancer

Histopathological examination (biopsy) is the "gold standard" for the diagnosis of colorectal cancer (CRC). However, biopsy is an invasive method, and due to the temporal and spatial heterogeneity of the tumor, a single biopsy cannot reveal the comprehensive biological characteristics and dynamic changes of the tumor. Therefore, there is a need for new biomarkers to improve CRC diagnosis and to monitor and treat CRC patients. Numerous studies have shown that "liquid biopsy" is a promising minimally invasive method for early CRC detection. A liquid biopsy mainly samples circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA (miRNA) and extracellular vesicles (EVs). CTCs are malignant cells that are shed from the primary tumors and/or metastases into the peripheral circulation. CTCs carry information on both primary tumors and metastases that can reflect dynamic changes in tumors in a timely manner. As a promising biomarker, CTCs can be used for early disease detection, treatment response and disease progression evaluation, disease mechanism elucidation, and therapeutic target identification for drug development. This review will discuss currently available technologies for plasma CTC isolation and detection, their utility in the management of CRC patients and future research directions.

Combination of CT and telomerase+ circulating tumor cells improves diagnosis of small pulmonary nodules

BACKGROUND

Early diagnosis and treatment are key to the long-term survival of lung cancer patients. Although CT has significantly contributed to the early diagnosis of lung cancer, there are still consequences of excessive or delayed treatment. By improving the sensitivity and specificity of circulating tumor cell (CTC) detection, a solution was proposed for differentiating benign from malignant pulmonary nodules.

METHODS

In this study, we used telomerase reverse transcriptase–based (TERT-based) CTC detection (TBCD) to distinguish benign from malignant pulmonary nodules < 2 cm and compared this method with the pathological diagnosis as the gold standard. FlowSight and FISH were used to confirm the CTCs detected by TBCD.

RESULTS

Our results suggest that CTCs based on TBCD can be used as independent biomarkers to distinguish benign from malignant nodules and are significantly superior to serum tumor markers. When the detection threshold was 1, the detection sensitivity and specificity of CTC diagnosis were 0.854 and 0.839, respectively. For pulmonary nodules ≤ 1 cm and 1–2 cm, the sensitivity and specificity of CTCs were both higher than 77%. Additionally, the diagnostic ability of CTC-assisted CT was compared by CT detection. The results show that CT combined with CTCs could significantly improve the differentiation ability of benign and malignant nodules in lung nodules < 2 cm and that the sensitivity and specificity could reach 0.899 and 0.839, respectively.

CONCLUSION

TBCD can effectively diagnose pulmonary nodules and be used as an effective auxiliary diagnostic scheme for CT diagnosis.

FUNDING

National Key Research and Development Project grant nos. 2019YFC1315700 and 2017YFC1308702, CAMS Initiative for Innovative Medicine grant no. 2017-I2M-1-005, and National Natural Science Foundation of China grant no. 81472013.

Predictive Value of Folate Receptor-Positive Circulating Tumor Cells for the Preoperative Diagnosis of Lymph Node Metastasis in Patients with Lung Adenocarcinoma

Noninvasive assessments of the risk of lymph node metastasis (LNM) in patients with lung adenocarcinoma (LAD) are of great value for selecting individualized treatment options. However, the diagnostic accuracies of different preoperative LN evaluation methods in routine clinical practice are not satisfactory. Here, an assessment to detect folate receptor (FR)-positive circulating tumor cells (CTCs) based on ligand-targeted enzyme-linked polymerization is established. FR-positive CTCs have the potential to improve the specificity and sensitivity of diagnosing LNM in lung cancer patients. The addition of CTC level improved the diagnostic efficiency of the initial prediction model that comprises other clinical parameters. A nomogram for predicting preoperative LNM is established, which showed good prediction and calibration capacities and achieved an average area under the curve of 0.786. Good correlations are observed between the CTC level and nodal classifications, such as the number of positive LNs and the ratio of the number of positive LNs to removed LNs (LN ratio or LNR). The ligand-targeted enzyme-linked polymerization-assisted assessment of CTCs enables noninvasive detection and has a useful predictive value for the preoperative diagnosis of LNM in patients with LAD.

Circulating tumor cells can predict the prognosis of patients with non-small cell lung cancer after resection: a retrospective study

Background

The development of metastasis is the primary cause of death in patients with non-small cell lung cancer (NSCLC). However, identifying those NSCLC patients who will have loco-regional or distant disease recurrence after surgery is still challenging. Circulating tumor cells (CTCs) can accurately reflect the impact of micro-metastasis of tumor cells in circulating blood on patients’ treatment and prognosis. The aim of the present study was to explore the value of preoperative CTC concentration in predicting postoperative metastasis and recurrence risk in patients with NSCLC.

Methods

This study enrolled 347 patients with stage I–IIIA NSCLC. The CTCs were isolated using folate receptor (FR) positivity from peripheral blood samples before surgery, and then enriched and analyzed. Patients were divided into two groups for retrospective survival analysis based on the geometric mean of CTC concentration. The primary study endpoint was recurrence-free survival. Spearman’s correlation was used to evaluate the relationship between CTC concentration and clinical characteristics of NSCLC patients. A nomogram based on the multivariate Cox regression model was developed to predict recurrence and metastasis in the NSCLC patients. The performance of the nomogram was evaluated using the concordance index, calibration curve, and Hosmer-Lemeshow test.

Results

The median follow-up time was 38 months. Preoperative CTC concentration was not significantly related to tumor-node-metastasis staging (P>0.05) and was an independent prognostic factor for NSCLC patients [hazard ratio (HR), 5.489; 95% confidence interval (CI): 2.660–11.326, P<0.001]. The nomogram based on preoperative CTC concentration had a concordance index value of 0.82. Validation revealed that the nomogram possessed excellent predictive ability and calibration.

Conclusions

Preoperative CTC concentration is an independent and sensitive biomarker of prognosis in patients with NSCLC. Our nomogram based on preoperative CTC concentration is an effective and non-invasive tool for predicting the recurrence and metastasis of NSCLC.