Latest advances in clinical studies of circulating tumor cells in early and metastatic breast cancer

Circulating tumor cells in solid malignancies: From advanced isolation technologies to biological understanding and clinical relevance in early diagnosis and prognosis

Circulating tumor cells (CTCs) are shed from primary tumors and travel through the body via circulation, eventually settling to form micrometastases under favorable conditions. Numerous studies have identified CTCs as a negative prognostic indicator for survival across various cancer types. CTCs mirror the current heterogeneity and genetic and biological state of tumors, making their study invaluable for understanding tumor progression, cell senescence, and cancer dormancy. However, their isolation and characterization still poses a major challenge that limits their clinical translation. A wide array of methods, each with different levels of specificity, utility, cost, and sensitivity, have been developed to isolate and characterize CTCs. Moreover, innovative techniques are emerging to address the limitations of existing methods. In this review, we provide insights into CTC biology addressing spectra of markers employed for molecular analysis and functional characterization. It also emphasizes current label-dependent and label-independent isolation procedures, addressing their strengths and limitations. SIGNIFICANCE: A comprehensive overview of CTC biology, their molecular and functional characterization, along with their current clinical utility will help in understanding the present-day extent to which the clinical potential of CTCs is getting tapped in personalized medicine.

Circulating Tumor Cells: Pathological, Molecular and Functional Characteristics

This Special Issue, 'Circulating Tumor Cells: Pathological, Molecular and Functional Characteristics 1 [...].

Longitudinal analysis of circulating tumor cell numbers improves tracking metastatic breast cancer progression

Hormone-responsive breast cancer represents the most common type and has the best prognosis, but still approximately 40% of patients with this type can develop distant metastases, dramatically worsening the patient's survival. Monitoring metastatic breast cancer (mBC) for signs of progression is an important part of disease management. Circulating tumor cell (CTC) detection and molecular characteristics gain importance as a diagnostic tool, but do not represent a clinical standard and its value as a predictor of progression is not yet established. The main objective of this study was to estimate the prognostic value of not only the CTC numbers, but also the dynamics of the CTC numbers in the same patient during the continuous evaluation of CTCs in patients with advanced breast cancer. The other objective was to assess the molecular changes in CTCs compared to primary tumor samples by genetic analysis of the seven genes associated with estrogen signaling pathway, mutations in which are often responsible for the resistance to endocrine therapy, and subsequent progression. This approach was taken to evaluate if genetic analysis of CTCs can be used in tracking the resistance, signaling that hormonal therapy should be replaced. Consequently, this report presents the results of a longitudinal CTC study based on three subsequent blood collections from 135 patients with metastatic breast cancer, followed by molecular analysis of the isolated single CTCs. CTCs were detected and isolated using an image-based, EpCAM-independent system CytoTrack; this approach allowed evaluation of EpCAM expression in detected CTCs. Isolated CTCs were subjected to NGS analysis to assess mutational changes. The results confirm the importance of the status of the CTC for progression-free survival and overall survival and provide new data on the dynamics of the CTC during a long monitoring period and in relation to clinical progression, highlighting the advantage of constant monitoring over the single count of CTC. Furthermore, high genetic and phenotypic inter- and intrapatient heterogeneity observed in CTCs suggest that metastatic lesions are divergent. High genetic heterogeneity in the matching CTC/primary tumor samples may indicate early dissemination. The tendency towards the accumulation of activating/oncogenic mutation in CTCs, leading to anti-estrogen resistant disease, was not confirmed in this study.

Exploring the Immunological Profile in Breast Cancer: Recent Advances in Diagnosis and Prognosis through Circulating Tumor Cells

This review offers a comprehensive exploration of the intricate immunological landscape of breast cancer (BC), focusing on recent advances in diagnosis and prognosis through the analysis of circulating tumor cells (CTCs). Positioned within the broader context of BC research, it underscores the pivotal role of the immune system in shaping the disease's progression. The primary objective of this investigation is to synthesize current knowledge on the immunological aspects of BC, with a particular emphasis on the diagnostic and prognostic potential offered by CTCs. This review adopts a thorough examination of the relevant literature, incorporating recent breakthroughs in the field. The methodology section succinctly outlines the approach, with a specific focus on CTC analysis and its implications for BC diagnosis and prognosis. Through this review, insights into the dynamic interplay between the immune system and BC are highlighted, with a specific emphasis on the role of CTCs in advancing diagnostic methodologies and refining prognostic assessments. Furthermore, this review presents objective and substantiated results, contributing to a deeper understanding of the immunological complexity in BC. In conclusion, this investigation underscores the significance of exploring the immunological profile of BC patients, providing valuable insights into novel advances in diagnosis and prognosis through the utilization of CTCs. The objective presentation of findings emphasizes the crucial role of the immune system in BC dynamics, thereby opening avenues for enhanced clinical management strategies.

Think "HER2" different: integrative diagnostic approaches for HER2-low breast cancer

This work explores the complex field of HER2 testing in the HER2-low breast cancer era, with a focus on methodological aspects. We aim to propose clear positions to scientific societies, institutions, pathologists, and oncologists to guide and shape the appropriate diagnostic strategies for HER2-low breast cancer. The fundamental question at hand is whether the necessary tools to effectively translate our knowledge about HER2 into practical diagnostic schemes for the lower spectrum of expression are available. Our investigation is centered on the significance of distinguishing between an immunohistochemistry (IHC) score 0 and score 1+ in light of the clinical implications now apparent, as patients with HER2-low breast cancer become eligible for trastuzumab-deruxtecan treatment. Furthermore, we discuss the definition of HER2-low beyond its conventional boundaries and assess the reliability of established diagnostic procedures designed at a time when therapeutic perspectives were non-existent for these cases. In this regard, we examine potential complementary technologies, such as gene expression analysis and liquid biopsy. Ultimately, we consider the potential role of artificial intelligence (AI) in the field of digital pathology and its integration into HER2 testing, with a particular emphasis on its application in the context of HER2-low breast cancer.