Circulating tumor cells in solid cancer: Tumor marker of clinical relevance?

Abstract

Circulating tumor cells (CTC) can be detected in the peripheral blood of patients with a variety of solid cancers. Because of their very low frequency, these tumor cells are not easily detected using conventional cytology methods. In the past decade, numerous groups have attempted to detect CTC of solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction, which has been shown to be superior to conventional techniques. However, the biological significance of CTC and the therapeutic relevance of their detection are still debated. This article reviews the most recent findings on this subject, and discusses the potential of identification and molecular characterization of the subset of CTC responsible for metastasis development. Confirming the prognostic value of CTC would provide clinicians with a unique tool for better stratification of patients' risk and provide basic researchers with a new target for the development of novel therapeutic approaches.

Enumeration, characterization, and collection of intact circulating tumor cells by cross contamination‐free flow cytometry

“…A large body of clinical studies has indicated that circulating tumor cells (CTC) in peripheral blood are an important prognostic marker for cancers (1)(2)(3)(4)(5). The presence of CTC in the peripheral blood of patients has been implicated in tumor progression and metastasis development.…”

Using detection of survivin‐expressing circulating tumor cells in peripheral blood to predict tumor recurrence following curative resection of gastric cancer

“…Patients who undergo potentially curative surgeries retain the risk of recurrence that originates from microscopic tumor residues known as minimal residual disease (MRD). MRD can affect different body compartments, including bone marrow, lymph nodes, and peripheral blood 7. Quantitative real‐time polymerase chain reaction (qrt‐PCR) is considered to be the most sensitive method for evaluating gene expression.…”

Survivin gene levels in the peripheral blood of patients with gastric cancer independently predict survival

“…These conflicting data might depend on the fact that CK19 and CEA are markers of CTC presence but not necessarily of CTC ability to metastasize: in fact, it is well accepted that only a subset of CTC has the biological potential of giving rise to metastatic deposits, while most CTC ultimately die without being harmful for the host [7]. Accordingly, markers of CTC "aggressiveness" such as Survivin might reveal to be more informative in terms of correlation with patients' prognosis.…”

“…Patients who had undergone potentially curative surgeries retain the risk of recurrence that originates from microscopic tumor residues known as minimal residual disease (MRD). MRD can affect different body compartments, including the bone marrow, lymph nodes and peripheral blood [7]. In recent years, several studies have focused on the detection of circulating tumor cells (CTC) with respect to their clinical implications for patients with gastric cancer.…”