Association Between Baseline Circulating Tumor Cells, Molecular Tumor Profiling, and Clinical Characteristics in a Large Cohort of Chemo-naïve Metastatic Colorectal Cancer Patients Prospectively Collected

Targeted Treatment against Cancer Stem Cells in Colorectal Cancer

The cancer stem cell (SC) theory proposes that a population of SCs serves as the driving force behind fundamental tumor processes, including metastasis, recurrence, and resistance to therapy. The standard of care for patients with stage III and high-risk stage II colorectal cancer (CRC) includes surgery and adjuvant chemotherapy. Fluoropyrimidines and their combination with oxaliplatin increased the cure rates, being able to eradicate the occult metastatic SC in a fraction of patients. The treatment for unresectable metastatic CRC is based on chemotherapy, antibodies to VEGF and EGFR, and tyrosine-kinase inhibitors. Immunotherapy is used in MSI-H tumors. Currently used drugs target dividing cells and, while often effective at debulking tumor mass, these agents have largely failed to cure metastatic disease. SCs are generated either due to genetic and epigenetic alterations in stem/progenitor cells or to the dedifferentiation of somatic cells where diverse signaling pathways such as Wnt/β-catenin, Hedgehog, Notch, TGF-β/SMAD, PI3K/Akt/mTOR, NF-κB, JAK/STAT, DNA damage response, and Hippo-YAP play a key role. Anti-neoplastic treatments could be improved by elimination of SCs, becoming an attractive target for the design of novel agents. Here, we present a review of clinical trials assessing the efficacy of targeted treatment focusing on these pathways in CRC.

Prognostic Effect of Performance Status on Outcomes of Patients with Colorectal Cancer Receiving First-Line Chemotherapy: A Meta-analysis

BACKGROUND

Performance status (PS) is a variable derived from the assessment of a patient's functional status, originally proposed to predict drug toxicity. However, despite its characteristic of being subjective and unidimensional, it has become one of the most important prognostic variables for patients with metastatic colorectal cancer (mCRC). In light of the considerable progressive prolongation of median overall survival (OS) of patients with mCRC, it is unclear whether PS continues to be a valid prognostic factor. This article aims to perform a meta-analysis to verify the current prognostic role of PS.

METHODS

A search on two databases of prospective trials of first-line chemotherapy in mCRC patients, published in English from 1991 to 2020, was done by predefined criteria. After the selection of phase III trials evaluating the prognostic role of PS, a meta-analysis has been performed.

RESULTS

Thirteen trials were included in the meta-analysis. They reported a reduction in the risk of death with a PS 0 compared to a PS 1 or more (HR 0.63, CI 0.54-0.72; 13 studies), which was confirmed for the comparison between PS 0 and PS 1. However, the study found significant heterogeneity (Q = 68.10; p-value < 0.001) and high-grade inconsistency (I2 = 82.38%). Therefore, to explore the reasons for the heterogeneity, a univariate meta-regression was performed, which suggested a possible moderating activity for liver metastases and timing of metastasis.

CONCLUSIONS

PS is a reliable prognostic factor for patients with mCRC receiving first-line chemotherapy but is poorly evaluated in phase III trials.

Circulating Tumor Cells: How Far Have We Come with Mining These Seeds of Metastasis?

Circulating tumor cells (CTCs) are cancer cells that slough off from the tumor and circulate in the peripheral blood and lymphatic system as micro metastases that eventually results in macro metastases. Through a simple blood draw, sensitive CTC detection from clinical samples has proven to be a useful tool for determining the prognosis of cancer. Recent technological developments now make it possible to detect CTCs reliably and repeatedly from a simple and straightforward blood test. Multicenter trials to assess the clinical value of CTCs have demonstrated the prognostic value of these cancer cells. Studies on CTCs have filled huge knowledge gap in understanding the process of metastasis since their identification in the late 19th century. However, these rare cancer cells have not been regularly used to tailor precision medicine and or identify novel druggable targets. In this review, we have attempted to summarize the milestones of CTC-based research from the time of identification to molecular characterization. Additionally, the need for a paradigm shift in dissecting these seeds of metastasis and the possible future avenues to improve CTC-based discoveries are also discussed.

Circulating Tumor Cells: From Basic to Translational Research

BACKGROUND

Metastasis is the leading cause of cancer-related deaths. Most studies have focused on the primary tumor or on overt metastatic lesions, leaving a significant knowledge gap concerning blood-borne cancer cell dissemination, a major step in the metastatic cascade. Circulating tumor cells (CTCs) in the blood of patients with solid cancer can now be enumerated and investigated at the molecular level, giving unexpected information on the biology of the metastatic cascade.

CONTENT

Here, we reviewed recent advances in basic and translational/clinical research on CTCs as key elements in the metastatic cascade.

SUMMARY

Findings from translational studies on CTCs have elucidated the complexity of the metastatic process. Fully understanding this process will open new potential avenues for cancer therapeutic and diagnostic strategies to propose precision medicine to all cancer patients.

Utilization of Circulating Tumor Cells in the Management of Solid Tumors

Circulating tumor cells (CTCs) are tumor cells shed from the primary tumor into circulation, with clusters of CTCs responsible for cancer metastases. CTC detection and isolation from the bloodstream are based on properties distinguishing CTCs from normal blood cells. Current CTC detection techniques can be divided into two main categories: label dependent, which depends upon antibodies that selectively bind cell surface antigens present on CTCs, or label-independent detection, which is detection based on the size, deformability, and biophysical properties of CTCs. CTCs may play significant roles in cancer screening, diagnosis, treatment navigation, including prognostication and precision medicine, and surveillance. In cancer screening, capturing and evaluating CTCs from peripheral blood could be a strategy to detect cancer at its earliest stage. Cancer diagnosis using liquid biopsy could also have tremendous benefits. Full utilization of CTCs in the clinical management of malignancies may be feasible in the near future; however, several challenges still exist. CTC assays currently lack adequate sensitivity, especially in early-stage solid malignancies, due to low numbers of detectable CTCs. As assays improve and more trials evaluate the clinical utility of CTC detection in guiding therapies, we anticipate increased use in cancer management.

Circulating tumour cells in gastrointestinal cancers: food for thought?

Gastrointestinal (GI) cancers account for 35% of cancer-related deaths, predominantly due to their ability to spread and generate drug-tolerant metastases. Arising from different locations in the GI system, the majority of metastatic GI malignancies colonise the liver and the lungs. In this context, circulating tumour cells (CTCs) are playing a critical role in the formation of new metastases, and their presence in the blood of patients has been correlated with a poor outcome. In addition to their prognostic utility, prospective targeting of CTCs may represent a novel, yet ambitious strategy in the fight against metastasis. A better understanding of CTC biology, mechanistic underpinnings and weaknesses may facilitate the development of previously underappreciated anti-metastasis approaches. Here, along with related clinical studies, we outline a selection of the literature describing biological features of CTCs with an impact on their metastasis forming ability in different GI cancers.

Association of Circulating Tumor Cells and Tumor Molecular Profile With Clinical Outcomes in Patients With Previously Untreated Metastatic Colorectal Cancer: A Pooled Analysis of the Phase III VISNÚ-1 and Phase II VISNÚ-2 Randomized Trials

BACKGROUND

The bCTC count is a well-established prognostic biomarker in mCRC, as well as in other tumor types. The aim of this analysis was to evaluate the prognostic/predictive role of the bCTC count (≥3 vs. <3) in previously untreated mCRC.

PATIENTS AND METHODS

The study involved 589 untreated mCRC patients included in the intention-to-treat population of 2 randomized clinical trials (phase III VISNU-1 [NCT01640405] and phase II VISNU-2 [NCT01640444] studies).

RESULTS

Of the 589 patients, 349 (59.2%) had bCTC≥3 and 240 (40.7%) had bCTC<3. Multivariate analysis showed that the bCTC count is an independent prognostic factor for overall survival (OS) (HR 0.59, 95% CI 0.48-0.72; P = 0.000) and potential for progression-free survival (PFS) (P = 0.0549). Median OS was 32.9 and 19.5 months in patients with bCTC<3 and bCTC≥3 (P <0.001), respectively. This effect was also observed comparing OS in RASwt patients from both studies. Other prognostic factors were: ECOG-PS, primary tumor site, number of metastatic sites and surgery of the primary tumor. Median OS was lower for patients treated with anti-VEGF versus anti-EGFR (22.3 vs. 33.3 months, P <0.0001) while there were no significant differences in PFS according to the targeted treatment received.

CONCLUSION

This post-hoc analysis of 2 randomized studies confirms the poor prognosis of patients with bCTC≥3 but this is not associated with other adverse independent prognostic factors such as RAS/BRAF mutations.

Circulating Tumor Cells in Colorectal Cancer: Detection Systems and Clinical Utility

Colorectal cancer (CRC) is the third most common cancer worldwide. The high mortality from CRC is mainly related to metastasis affecting distant organs and their function. Dissemination of tumor cells from the primary tumor and hematogeneous spread are considered crucial in the formation of tumor metastases. The analysis of circulating tumor cells (CTCs) and CTC clusters in the blood can be used for the early detection of invasive cancer. Moreover, CTCs have a prognostic significance in the monitoring of a malignant disease or the response to chemotherapy. This work presents an overview of the research conducted on CTCs with the aim of finding suitable detection systems and assessing the possibility of clinical applications in patients with CRC.

Liquid Biopsies in Colorectal Liver Metastases: Towards the Era of Precision Oncologic Surgery

Tumor mutational analysis has been incorporated into the management of patients with CRLM since it can provide valuable prognostic information as well as guide peri-operative systemic treatment. Unlike tumor biopsy, liquid biopsy has emerged as a promising, non-invasive alternative that can detect cell-derived markers from a variety of body fluids and might better characterize all subclones present at a specific time point and allow sequential monitoring of disease evolution. Although not currently considered standard of care, an increasing number of cancer centers are nowadays routinely using liquid biopsies in the treatment of CRLM patients with promising results. The current review provides an overview of liquid biopsies in cancer therapeutics and focuses on the application of this relatively new approach on patients with CRLM.

Detection of circulating tumor cells: opportunities and challenges

Circulating tumor cells (CTCs) are cells that shed from a primary tumor and travel through the bloodstream. Studying the functional and molecular characteristics of CTCs may provide in-depth knowledge regarding highly lethal tumor diseases. Researchers are working to design devices and develop analytical methods that can capture and detect CTCs in whole blood from cancer patients with improved sensitivity and specificity. Techniques using whole blood samples utilize physical prosperity, immunoaffinity or a combination of the above methods and positive and negative enrichment during separation. Further analysis of CTCs is helpful in cancer monitoring, efficacy evaluation and designing of targeted cancer treatment methods. Although many advances have been achieved in the detection and molecular characterization of CTCs, several challenges still exist that limit the current use of this burgeoning diagnostic approach. In this review, a brief summary of the biological characterization of CTCs is presented. We focus on the current existing CTC detection methods and the potential clinical implications and challenges of CTCs. We also put forward our own views regarding the future development direction of CTCs.

Association of miR-21 and miR-335 to microsatellite instability and prognosis in stage III colorectal cancer

BACKGROUND

MicroRNAs (miRs) are frequently altered in colorectal cancer (CRC) and can be used as prognostic factors.

OBJECTIVE

To confirm in stage III CRC patients a reported miR signature that was associated to the presence of metastatic disease. To correlate miR expression with microsatellite instability (MSI) and mutations in RAS and BRAF.

METHODS

miR-21, miR-135a, miR-206, miR-335 and miR-Let-7a expression was analyzed by RT-qPCR in 150 patients out of the 329 patients used to analyze MSI and RAS and BRAF mutations. Association with disease free survival (DFS) and overall survival (OS) was analyzed. Data was confirmed by a multivariate analysis.

RESULTS

MiR-21 high expression (p= 0.034) and miR-335 low expression (p= 0.0061) were significantly associated with MSI-H. A positive trend (p= 0.0624) between miR-135a high expression and RAS mutations was found. Lower miR-21 expression levels are associated with DFS (HR = 2.654, 95% CI: 1.066-6.605, p= 0.036) and a trend with OS (HR = 2.419, 95% CI: 0.749-7.815, p= 0.140). MiR-21 high expression significantly improves DFS of the poor prognosis group (T4 or N2) (p= 0.03).

CONCLUSIONS

Association of increased expression of miR-21 and better prognosis in the poor prognostic group may be of interest and could be explored in future prospective clinical trials.

Upfront primary tumour resection and survival in synchronous metastatic colorectal cancer according to primary tumour location and RAS status: Pooled analysis of the Spanish Cooperative Group for the Treatment of Digestive Tumours (TTD)

INTRODUCTION

Retrospective studies and meta-analyses suggest that upfront primary tumour resection (UPTR) confers a survival benefit in patients with asymptomatic unresectable metastatic colorectal cancer (mCRC) undergoing chemotherapy, however a consensus of its role in routine clinical practice in the current era of targeted therapies is lacking. This retrospective study aimed to analyse the survival benefit of UPTR in terms of tumour location and mutational status, in patients with synchronous mCRC receiving chemotherapy and targeted therapy.

PATIENTS AND METHODS

Survival was analysed in a pooled cohort of synchronous mCRC patients treated with a first-line anti-VEGF or anti-EGFR inhibitor in seven trials of the Spanish TTD group, according to UPTR, tumour-sidedness and mutational profiling.

RESULTS

Of 1334 eligible patients, 642 (48%) had undergone UPTR. UPTR was associated with significantly longer overall survival (OS; 25.0 vs 20.3 months; HR 1.30, 95%CI 1.15-1.48; p < 0.0001). UPTR was associated with significant OS benefit in both left-sided (HR 1.38, 95%CI 1.13-1.69; p = 0.002) and right-sided (HR 1.39, 95%CI 1.00-1.94; p = 0.049) tumours, RASwt (HR 1.29, 95%CI 1.05-1.60; p = 0.016) and BRAFwt (HR 1.49, 95%CI 1.21-1.84; p = 0.0002) tumours, and treatment with anti-EGFRs (HR 1.47, 95%CI 1.13-1.92; p = 0.004) and anti-VEGFs (HR 1.25, 95%CI 1.08-1.44; p = 0.003). Multivariate analysis identified number of metastatic sites, RAS status, primary tumour location and UPTR as independent prognostic factors for OS.

CONCLUSION

Considering the selection bias inherent to this study, our results support UPTR before first-line anti-EGFR or anti-VEGF targeted therapy in right and left-sided asymptomatic unresectable synchronous mCRC patients. RAS/BRAF mutational status may also influence UPTR function.

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.

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.

Clinical Relevance of Viable Circulating Tumor Cells in Patients with Metastatic Colorectal Cancer: The COLOSPOT Prospective Study

Simple Summary

The analysis of circulating tumor cells (CTCs) as a “real-time liquid biopsy” in epithelial tumors for personalized medicine has received tremendous attention over the past years, with important clinical implications. In metastatic colorectal cancer (mCRC), the CellSearch^® system has already demonstrated its prognostic value and interest in monitoring treatment response, but the number of recovered CTCs remains low. In this article, we evaluate the early prognostic and predictive value of viable CTCs in patients with mCRC treated with FOLFIRI–bevacizumab with an alternative approach, the functional EPISPOT assay. This study shows that viable CTCs can be detected in patients with mCRC before and during FOLFIRI–bevacizumab treatment and that CTC detection at D₂₈ and the D₀–D₂₈ CTC kinetics evaluated with the EPISPOT assay are associated with response to treatment.

Abstract

Background: Circulating tumor cells (CTCs) allow the real-time monitoring of tumor course and treatment response. This prospective multicenter study evaluates and compares the early predictive value of CTC enumeration with EPISPOT, a functional assay that detects only viable CTCs, and with the CellSearch^® system in patients with metastatic colorectal cancer (mCRC). Methods: Treatment-naive patients with mCRC and measurable disease (RECIST criteria 1.1) received FOLFIRI–bevacizumab until progression or unacceptable toxicity. CTCs in peripheral blood were enumerated at D₀, D₁₄, D₂₈, D₄₂, and D₅₆ (EPISPOT assay) and at D₀ and D₂₈ (CellSearch^® system). Progression-free survival (PFS) and overall survival (OS) were assessed with the Kaplan–Meier method and log-rank test. Results: With the EPISPOT assay, at least 1 viable CTC was detected in 21% (D₀), 15% (D₁₄), 12% (D₂₈), 10% (D₄₂), and 12% (D₅₆) of 155 patients. PFS and OS were shorter in patients who remained positive, with viable CTCs between D₀ and D₂₈ compared with the other patients (PFS = 7.36 vs. 9.43 months, p = 0.0161 and OS = 25.99 vs. 13.83 months, p = 0.0178). The prognostic and predictive values of ≥3 CTCs (CellSearch^® system) were confirmed. Conclusions: CTC detection at D₂₈ and the D₀–D₂₈ CTC dynamics evaluated with the EPISPOT assay were associated with outcomes and may predict response to treatment.

Liquid Biopsy for Prognosis and Treatment in Metastatic Colorectal Cancer: Circulating Tumor Cells vs Circulating Tumor DNA

Liquid biopsy recently gained widespread attention as a noninvasive alternative/complementary technique to tissue biopsy in patients with cancer. As technological advances have improved both feasibility and turnaround time, liquid biopsy has expanded tumor molecular analysis with acknowledgement of both spatial and temporal heterogeneity, overcoming many limitations of traditional tissue biopsy. Because of its diagnostic, prognostic, and predictive value, liquid biopsy has been extensively studied also in metastatic colorectal cancer. Indeed, as personalized medicine establishes its role in cancer treatment, genetic biomarkers unveiling the emergence of early resistance are needed. Among the wide variety of tumor analytes amenable to collection, circulating DNA and circulating tumor cells are the most adopted approaches, and both carry clinical relevance in colorectal cancer. However, few studies focused on comparing feasibility between these two approaches. In this review, we discuss the potential implications of liquid biopsy in metastatic colorectal cancer, assessing the advantages and drawbacks of circulating DNA and circulating tumor cells, and highlighting the most relevant trials for clinical practice.

Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors

Despite advances in screening and therapeutics cancer continues to be one of the major causes of morbidity and mortality worldwide. The molecular profile of tumor is routinely assessed by surgical or bioptic samples, however, genotyping of tissue has inherent limitations: it represents a single snapshot in time and it is subjected to spatial selection bias owing to tumor heterogeneity. Liquid biopsy has emerged as a novel, non-invasive opportunity of detecting and monitoring cancer in several body fluids instead of tumor tissue. Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), RNA (mRNA and microRNA), microvesicles, including exosomes and tumor "educated platelets" were recently identified as a source of genomic information in cancer patients which could reflect all subclones present in primary and metastatic lesions allowing sequential monitoring of disease evolution. In this review, we summarize the currently available information concerning liquid biopsy in breast cancer, colon cancer, lung cancer and melanoma. These promising issues still need to be standardized and harmonized across laboratories, before fully adopting liquid biopsy approaches into clinical practice.

Measurement of Portal Vein Blood Circulating Tumor Cells is Safe and May Correlate With Outcomes in Resected Pancreatic Ductal Adenocarcinoma

BACKGROUND

This study investigated the safety and feasibility of intraoperative portal vein blood (PVB) collection at the time of pancreatic ductal adenocarcinoma (PDAC) resection. Relationships of circulating tumor cells (CTCs) in PVB and peripheral blood (PB) with overall survival (OS) and recurrence-free survival were studied.

METHODS

Patients undergoing PDAC resection were offered enrollment in a prospective liquid biopsy protocol. The patients had PB drawn before incision and PVB drawn before tumor mobilization, then again immediately after resection. Using standard CellSearch protocols, CTCs were identified and compared with OS.

RESULTS

Of the 34 patients enrolled in this study, 23 (68%) underwent pancreaticoduodenectomy, 8 (23%) underwent distal pancreatectomy, and 3 (9%) underwent total pancreatectomy. Peripheral blood was available for 22 (65%) and PVB for 31 (91%) of the patients. No bleeding or thrombotic complications occurred with the PVB draws. The CTC counts per 7.5 mL of PVB collected before and after resection were highly correlated (R² = 0.89). The study found CTCs in 11 (50%) of 22 PB samples and 22 (71%) of 31 PVB samples. The OS rate at 18 months was 92% for the patients with < 3 CTCs, 71% for the patients with ≥ 3 CTCs per 7.5 mL of PB (p = 0.30), 100% for the patients without PVB CTCs, and 70% for the patients with PVB CTCs (p < 0.01).

CONCLUSIONS

Collection of PVB during PDAC resection is safe. In this pilot study, PVB CTC counts but not PB CTC counts were significantly correlated with OS. This opens the door for future studies on selective omission of adjuvant chemotherapy for patients treated preoperatively and tailored surveillance intensity for patients without PVB CTCs at PDAC resection.

Liquid biopsy as a perioperative biomarker of digestive tract cancers: review of the literature

Tissue biopsies are the gold-standard for investigating the molecular characterization of tumors. However, a "solid" biopsy is an invasive procedure that cannot capture real-time tumor dynamics and may yield inaccurate information because of intratumoral heterogeneity. In this review, we summarize the current state of knowledge about surgical treatment-associated "liquid" biopsy for patients with digestive organ tumors. A liquid biopsy is a technique involving the sampling and testing of non-solid biological materials, including blood, urine, saliva, and ascites. Previous studies have reported the potential value of blood-based biomarkers, circulating tumor cells, and cell-free nucleic acids as facilitators of cancer treatment. The applications of a liquid biopsy in a cancer treatment setting include screening and early diagnosis, prognostication, and outcome and recurrence monitoring of cancer. This technique has also been suggested as a useful tool in personalized medicine. The transition to precision medicine is still in its early stages. Soon, however, liquid biopsy is likely to form the basis of patient selection for molecular targeted therapies, predictions regarding chemotherapy sensitivity, and real-time evaluations of therapeutic effects.