Circulating Tumor Cells: Applications in Cytopathology

Liquid biopsy: An innovative tool in oncology. Where do we stand?

The Liquid Biopsy (LB) represents an ideal surrogate of tumor Tissue Biopsy (TB) when the aim is to obtain useful information on patient prognosis and personalized therapy. This technique renders it possible to isolate circulating tumor cells, circulating tumor DNA and other molecules from biological fluids. The most commonly used fluid for liquid biopsy is blood, but depending on the case it could be necessary to isolate the tumor components from other biological fluids such as urine, pleural effusion, cerebrospinal fluid, and others. The main advantages of liquid biopsy are the minimally invasive nature of the procedure and the possibility of analyzing all tumor clones. Limitations include difficulties in the isolation of tumor components and the requirement for highly sensitive analysis methods to avoid the risk of technical artifacts. In our review we will focus on describing circulating tumor biomarkers to illustrate the variety of information that can be obtained from biological fluids, particularly blood. We will then discuss the advanced biotechnological techniques suitable for the identification and analysis of Circulating Tumor DNA (ctDNA), examining both the potential and limitations of analytical methods and the clinical applicability of liquid biopsy for cancer diagnosis, monitoring, and therapeutic prediction. Additionally, we will explore strategies to enhance this valuable alternative to the more invasive tissue biopsy, with a dedicated focus on ongoing clinical studies, currently approved tests, and guideline recommendations.

Different Liquid Biopsies for the Management of Non-Small Cell Lung Cancer in the Mutational Oncology Era

In the last ten years, liquid biopsy has been slowly joining the traditional invasive techniques for the diagnosis and monitoring of tumors. Liquid biopsies allow easy repeated sampling of blood, reflect the tumor scenario, and make personalized therapy real for the patient. Liquid biopsies isolate and utilize different substrates present in patients' body fluids such as circulating tumor cells, circulating tumor DNA, tumor extracellular vesicles, etc. One of the most-used solid cancers in the development of the non-invasive liquid biopsy approach that has benefited from scientific advances is non-small cell lung cancer (NSCLC). Using liquid biopsy, it is possible to have more details on NSCLC staging, progression, heterogeneity, gene mutations and clonal evolution, etc., basing the treatment on precision medicine as well as on the screening of markers for therapeutic resistance. With this review, the authors propose a complete and current overview of all different liquid biopsies available to date, to understand how much has been carried out and how much remains to be completed for a better characterization of NSCLC.

Detection of Circulating Tumor Cells and Epithelial Progenitor Cells: A Comprehensive Study

Technological advancement to enhance tumor cells (TC) has allowed discovery of various cellular bio-markers: cancer stem cells (CSC), circulating tumor cells (CTC), and endothelial progenitor cells (EPC). These are responsible for resistance, metastasis, and premetastatic conditions of cancer. Detection of CSC, CTC, and EPC assists in early diagnosis, recurrence prediction, and treatment efficacy. This review describes various methods to detect TC subpopulations such as in vivo assays (sphere-forming, serial dilution, and serial transplantation), in vitro assays (colony-forming cells, microsphere, side-population, surface antigen staining, aldehyde dehydrogenase activity, and Paul Karl Horan label-retaining cells, surface markers, nonenriched and enriched detection), reporter systems, and other analytical methods (flow cytometry, fluorescence microscopy/spectroscopy, etc.). The detailed information on methods to detect CSC, CTC, and EPC in this review will assist investigators in successful prognosis, diagnosis, and cancer treatment with greater ease.

Minimal residual disease assessment of papillary thyroid carcinoma through circulating tumor cell-based cytology

The overall estimated risk of recurrence after an apparently complete thyroid cancer resection ranges from <1% to 55%, and the high-quality pathology report is crucial for proper risk stratification. The neck ultrasound (US) and serum thyroglobulin (Tg) and anti-Tg antibody (TgAb) assays are the mainstays for Differentiated Thyroid Cancer (DTC) follow-up. However, the neck US includes a high frequency of nonspecific findings and despite the serum, Tg unmasks the presence of thyrocytes, it is not discriminating between normal and malignant cells. In this study, to improve post-surgery follow-up of minimal residual disease in papillary thyroid cancer (PTC) patients, blood-derived cytology specimens were evaluated for the presence of circulating tumor cells (CTCs). The presence of CTCs of thyroid origin was confirmed by cytomorphological and tissue-specific antigens analysis (Thyroid Transcription Factor-1/TTF-1 and Tg) and proliferative profile (percentage of cells in S-phase). Our data revealed an unfavorable' prognostic risk in patients with >5% CTCs (p = 0.09) and with >30% S-phase cells at baseline (p = 0.0015), predicting ≤1 year relapsing lesion event. These results suggest a new intriguing frontier of precision oncology forefront cytology-based liquid biopsy.

Coagulation and inflammation in cancer: Limitations and prospects for treatment

The development of so-called immune checkpoint inhibitors (ICIs), which target specific molecular processes of tumour growth, has had a transformative effect on cancer treatment. Widespread use of antibody-based medicines to inhibit tumour cell immune evasion by modulating T cell responses is becoming more common. Despite this, response rates are still low, and secondary resistance is an issue that arises often. In addition, a wide range of serious adverse effects is triggered by enhancing the immunological response. As a result of an increased mortality rate, a higher prevalence of thrombotic complications is connected with an increased incidence of immunological reactions, complement activation, and skin toxicity. This suggests that the tumour microenvironment's interaction between coagulation and inflammation is important at every stage of the tumour's life cycle. The coagulation system's function in tumour formation is the topic of this review. By better understanding the molecular mechanisms in which tumour cells circulate, plasmatic coagulation and immune system cells are engaged, new therapy options for cancer sufferers may be discovered.

New Trends in the Detection of Gynecological Precancerous Lesions and Early-Stage Cancers

The prevention and early diagnostics of precancerous stages are key aspects of contemporary oncology. In cervical cancer, well-organized screening and vaccination programs, especially in developed countries, are responsible for the dramatic decline of invasive cancer incidence and mortality. Cytological screening has a long and successful history, and the ongoing implementation of HPV triage with increased sensitivity can further decrease mortality. On the other hand, endometrial and ovarian cancers are characterized by a poor accessibility to specimen collection, which represents a major complication for early diagnostics. Therefore, despite relatively promising data from evaluating the combined effects of genetic variants, population screening does not exist, and the implementation of new biomarkers is, thus, necessary. The introduction of various circulating biomarkers is of potential interest due to the considerable heterogeneity of cancer, as highlighted in this review, which focuses exclusively on the most common tumors of the genital tract, namely, cervical, endometrial, and ovarian cancers. However, it is clearly shown that these malignancies represent different entities that evolve in different ways, and it is therefore necessary to use different methods for their diagnosis and treatment.

Circulating Tumor Cells in Diagnosis and Treatment of Lung Cancer

Circulating tumor cells (CTCs), detached from the primary tumor or metastases and shed in the patient's bloodstream, represent a relatively easily obtainable sample of the cancer tissue that can indicate the actual state of cancer, and their evaluation can be repeated many times during the course of treatment. As part of liquid biopsy, evaluation of CTCs provides a lot of clinically relevant information, which reflects the actual, real-time conditions of the disease. CTCs can be used in cancer diagnosis or screening, real-time long-term disease monitoring and even therapy guidance. Their analysis can include their number, morphology, and biological features by using immunocytochemistry and all "-omic" technologies. This review describes methods of CTC isolation and potential clinical utilization in lung cancer.

Liquid Biopsy: General Concepts

Liquid biopsy provides the opportunity of detecting, analyzing and monitoring cancer in various body effluents such as blood or urine instead of a fragment of cancer tissue. It is composed of different biological matrices such as circulating tumor cells (CTCs), cell free nucleic acids, exosomes or tumors "educated platelets." In addition to representing a non- or minimally invasive procedure, it should represent a better view of tumor heterogeneity and allows for real-time monitoring of cancer evolution. Recent technological and molecular advances, greatly facilitated by the use of microfluidics in many cases, have permitted large progresses both in our ability to purify and analyze liquid biopsy components. In particular, the great developments of droplet-based digital PCR and the various optimizations of next generation sequencing technologies are central to the several validations of CTC-free DNA as a strong cancer biomarker. However, complete adoption of liquid biopsy in clinics will require pursuing recent efforts in the standardization of procedures both on the pre-analytical and analytical aspects.

Circulating Tumor Cell Detection in Lung Cancer: But to What End?

The understanding of the natural history and biology of lung cancer has been enhanced by studies into circulating tumor cells (CTCs). Fundamental and translational research, as well as clinical trials in the characterization and behavior of these cells, have constantly contributed to improving understanding within the domain of thoracic oncology. However, the use of these CTCs as prognostic and predictive biomarkers has not been adopted to the same extent as circulating free DNA (cf-DNA) in plasma, in the daily practice of thoracic oncologists. However, recent technological advances have firmly put the detection and characterization of CTCs in thoracic oncology back on the agenda, and have opened up perspectives for their routine clinical use. This review discusses the major advances of using CTCs in the domain of thoracic oncology, as well as the envisaged short- and long-term prospects.