Liquid biopsy for colorectal cancer screening: chances and challenges

Article information

Intest Res. 2026;.ir.2026.00080

Publication date (electronic) : 2026 July 6

doi : https://doi.org/10.5217/ir.2026.00080

Hyoung Il Choi¹, Jae Myung Cha^,1,2

¹Department of Gastroenterology, Kyung Hee University Hospital at Gangdong, Seoul, Korea

²Department of Gastroenterology, School of Medicine, Kyung Hee University, Seoul, Korea

Correspondence to Jae Myung Cha, Department of Gastroenterology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, 892 Dongnam-ro, Gangdong-gu, Seoul 05278, Korea. E-mail: drcha@khu.ac.kr

Received 2026 March 9; Revised 2026 April 23; Accepted 2026 May 4.

Abstract

INTRODUCTION

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and second leading cause of cancer-related death worldwide [1]. According to the Global Cancer Observatory database, substantial regional differences in CRC incidence have been observed worldwide [2]. In 2022 alone, 1,926,425 new CRC cases and 904,019 CRC-related deaths were reported globally, with the highest burden in Eastern Asia. If incidence rates remain unchanged from 2022, the number of new CRC cases is projected to reach 2.36 million by 2050, representing a 22.5% increase [2]. Furthermore, age-standardized mortality rates in Eastern Asia have approached those in Europe and have already surpassed those in North America. These findings highlight the substantial challenges of CRC screening in Eastern Asia, including Korea.

Organized CRC screening programs have been implemented in many countries and have demonstrated reductions in CRC incidence and mortality through the early detection of cancer and the removal of precancerous lesions [³]. Currently, the most widely used CRC screening modalities include fecal immunochemical testing (FIT), stool DNA testing, and colonoscopy. However, each screening modality has important limitations related to diagnostic performance, participation rates, and resource requirements. In recent years, advances in molecular technologies have enabled the detection of tumor-derived components in peripheral blood, giving rise to the concept of liquid biopsy. This review summarizes the biological rationale of liquid biopsy, recent advances in blood-based biomarkers for CRC detection, and emerging evidence from clinical studies. In addition, we discuss the chances and challenges associated with the integration of liquid biopsy into organized CRC screening programs.

LIMITATIONS OF CURRENT CRC SCREENING

Despite the proven reduction in mortality associated with organized CRC screening strategies, the current screening program has several important limitations. The effectiveness of organized CRC screening depends primarily on sustained participation. However, the real-world adoption of FIT is frequently less than 60%, even in countries with established national programs. Large population-based studies have shown that participation declines across repeated screening rounds, with longitudinal adherence being substantially lower than that in the first round [3,4]. Reduced repeat participation attenuates cumulative program sensitivity and limits long-term mortality benefits. Socioeconomic disadvantages, lower educational attainment, and limited health literacy are consistently associated with lower screening participation [5,6]. Although FIT demonstrates good sensitivity for CRC, meta-analyses have reported that FIT sensitivity for advanced precancerous lesions is substantially lower than that achieved using invasive screening modalities [7,8]. In addition, FIT detection is particularly limited for flat, nonpolypoid, and proximally located neoplasia, as well as serrated lesions. Given that CRC prevention depends on the identification and removal of advanced precancerous lesions, this limitation reduces the effectiveness of FIT-based programs.

Delays in diagnostic colonoscopy after a positive FIT are associated with increased CRC incidence and more advanced stages at diagnosis [4]. Thus, balancing screening test sensitivity with constraints in colonoscopy resources remains a critical challenge. In FIT-based screening programs, interval cancers may reflect false-negative stool test results and variability in colonoscopy quality. Landmark studies have demonstrated that the adenoma detection rate on colonoscopy is strongly associated with subsequent interval CRC risk and CRC-related mortality [9,10]. In organized screening strategies, colonoscopy quality may be more variable, depending on the extent of bowel preparation and complete examination; furthermore, operator-dependent variability contributes to residual risk [11]. Organized screening programs continue to demonstrate substantial variation in the socioeconomic status, race, ethnicity, and education level of participants. A recent systematic review showed that disadvantaged populations experience lower participation rates, longer delays in diagnostic colonoscopy, and higher CRC mortality [12]. Geographic disparities, including rural–urban differences and limited access to endoscopic services, further exacerbate inequities. In addition, colonoscopy in elderly patients has been associated with a higher likelihood of clinically significant findings but also an increased risk of procedure-related complications [13]. Therefore, careful patient selection, individualized bowel preparation, and tailored sedation strategies are essential to optimize the safety and effectiveness of colonoscopy in this vulnerable population [13].

Current organized CRC screening programs largely rely on age-based eligibility and FIT as a single-modality test [4,11,14]. For average-risk adults, an annual FIT is recommended by the American Cancer Society and the U.S. Preventive Services Task Force [15,16]. FIT is the most widely adopted because it is noninvasive, inexpensive, and scalable [3,4]. In population-based settings, FIT has consistently been associated with reduced CRC mortality. However, FIT has important limitations that should be considered, including lower sensitivity for advanced precancerous lesions, variable test performance depending on the selected hemoglobin cutoff, suboptimal adherence to repeated annual testing, and the need for timely diagnostic colonoscopy after a positive result (Table 1). Stool DNA testing offers higher sensitivity for CRC and advanced adenoma (AA) and allows for a longer screening interval [15,16]. The American Cancer Society recommends stool DNA testing every 3 years, whereas the U.S. Preventive Services Task Force recommends stool DNA testing every 1–3 years [15,16]. However, its implementation at the population level is limited by higher costs, lower specificity than FIT, greater logistical complexity in specimen collection and processing, and limited direct evidence demonstrating a reduction in CRC mortality (Table 1). Colonoscopy is the most comprehensive screening modality because it provides both diagnostic and preventive benefits and has high sensitivity for advanced precancerous lesions with a long screening interval [11]. However, population-level implementation of colonoscopy is constrained by its invasive nature, the need for bowel preparation and sedation, substantial demands on endoscopic capacity and workforce, higher cost, variability in quality, and lower participation rates [11].

Table 1.

Comparison of the Currently Available CRC Screening Modalities: FIT, Stool DNA Testing, and Blood-Based Liquid Biopsy

Participation is essential for effective CRC screening. However, higher participation alone does not guarantee improved clinical outcomes. The benefits of screening depend on participation and test performance. Tests with limited sensitivity, such as FIT, may miss early-stage CRC and advanced precancerous lesions, thereby attenuating stage shift and reducing mortality. The overall effectiveness of CRC screening is determined by the combined impact of population participation and diagnostic performance of the screening modality. Accordingly, neither FIT nor colonoscopy alone fully addresses the limitations of the currently organized CRC screening strategies. Currently, emerging blood-based biomarkers, multi-omics approaches, and artificial intelligence (AI)–integrated models have shown promise in early-phase studies [14]. Although these approaches have not yet been fully integrated into population-based, organized screening frameworks, the adoption of these emerging technologies into such programs may not be far off, given that the pace of scientific and technological advancement is accelerating rapidly.

LIQUID BIOPSY

Liquid biopsy refers to the analysis of tumor-derived components in blood or other body fluids to detect and characterize cancer in a minimally invasive manner [17]. Unlike conventional tissue biopsy, which requires invasive procedures and provides only a static snapshot of a single tumor site, liquid biopsy enables real-time and repeatable assessment of tumor presence, molecular characteristics, and dynamic changes during tumor evolution [17]. Because it can be performed through simple blood sampling, liquid biopsy is easier to repeat and imposes minimal physical burden on patients. In addition, liquid biopsy may better reflect tumor heterogeneity, as it captures tumor-derived material released from multiple primary and metastatic sites. Therefore, liquid biopsy may play a key role in future cancer screening, surveillance, and treatment monitoring, as it can detect early-stage cancer, tumor recurrence, or minimal residual disease after treatment; assess therapeutic efficacy by tracking changes in tumor burden; and contribute to determining prognosis by checking baseline and dynamic liquid biopsy profiles [17]. Furthermore, liquid biopsy can capture early molecular changes preceding clinical disease, as colorectal carcinogenesis is a multistep process involving genetic and epigenetic alterations (Fig. 1) [18]. Colorectal carcinogenesis leads to the release of tumor DNA into the bloodstream. Liquid biopsy can detect stable and circulating biomarkers and capture systemic representations of tumor heterogeneity from multiple tumor clones.

Fig. 1.

Biological rationale of liquid biopsy in colorectal carcinogenesis. Liquid biopsy can capture early molecular changes that precede clinical disease as colorectal carcinogenesis is a multistep process involving genetic and epigenetic alterations. Colorectal carcinogenesis leads to the release of tumor DNA into the bloodstream. Liquid biopsy can detect circulating biomarkers and capture a systemic representation of tumor heterogeneity deriving from multiple tumor clones. CTC, circulating tumor cell; ctDNA, circulating tumor DNA.

Molecular markers detectable by liquid biopsy include circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), cell-free DNA (cfDNA), circulating free RNA, and tumor-derived extracellular vesicles, such as exosomes [17]. Currently, most research efforts have focused on CTCs, ctDNA, cfDNA, and exosomes, as these components have demonstrated promising diagnostic and prognostic potential in CRC. CTCs are cells released from primary and metastatic tumors that are shed into blood vessels and circulate in the peripheral blood [17]. Although the proportion of CTCs in the blood is low, methods used for their detection or isolation are constantly being improved. CTCs play an increasingly important role in the diagnosis, detection, and prognosis of cancer. Nonetheless, a key challenge is how to isolate and collect CTCs more specifically. However, the rapid advancement of technology has further facilitated the clinical application of CTCs [19]. Because CTCs are present at extremely low concentrations in the bloodstream, liquid biopsy research has primarily focused on cfDNA and ctDNA. Although cfDNA is primarily derived from normal leukocytes and stromal cells, ctDNA accounts for approximately 0.1%–1% of total cfDNA and can dynamically reflect tumor burden at a given time point [20]. Compared with cfDNA, ctDNA has shorter base fragments and a shorter half-life, making it less affected by intra-tumor heterogeneity and more commonly used as a real-time tumor biomarker [21]. Therefore, ctDNA assays are widely used to monitor tumor burden dynamics and disease progression or prognosis. Exosomes are a subtype of extracellular vesicles that originate from endosomes and are released outside the cell after the fusion of multivesicular bodies with the cell membrane [10]. Exosomes are thus more closely integrated with clinical characteristics, such as molecular transport, immune responses, and the tumor microenvironment [22].

BIOMARKERS FOR CRC SCREENING

Currently available or investigational blood-based liquid biopsy tests for CRC screening are summarized in Table 2 [23-28]. Epi pro-Colon 2.0 CE (Epigenomics AG, Berlin, Germany) is a blood-based test designed to aid in the early detection of CRC [29]. The test comprises a qualitative assay for polymerase chain reaction (PCR)-based detection of methylated septin 9 (SEPT9) DNA, which can detect aberrant methylation specific to CRC [29,30]. The test discriminates between patients with CRC and healthy controls with high clinical sensitivity and specificity in pivotal case-control studies [29]. An early prospective study (PRESEPT study) evaluating methylated SEPT9 in asymptomatic individuals aged ≥50 years scheduled for screening colonoscopy achieved only 48.2% estimated sensitivity for CRC, ranging from 35.0% to 77.4% according to disease stage [23]. The study showed limited utility of blood-based methylated SEPT9 for population-based CRC screening due to limited sensitivity for detection of early cancers and AAs. However, a more recent meta-analysis including 29 studies showed promising data based on 10,486 subjects (3,202 patients with CRC and 7,284 controls) [24]. In this analysis, the 1/3 algorithm defined a positive result when at least 1 of the 3 PCR replicates was positive, whereas the 2/3 algorithm required at least 2 of the 3 replicates to be positive. Using these criteria, the pooled sensitivity of SEPT9 methylation for CRC detection was 0.74 (95% confidence interval [CI], 0.61–0.84) in the 1/3 algorithm group, while the specificity was 0.96 (95% CI, 0.95–0.97) in the 2/3 algorithm group. In addition, the area under the curve (AUC) for the diagnosis of CRC was 0.86 and 0.95 in 1/3 and 2/3 algorithm groups, respectively. Epi proColon 2.0 CE (Epigenomics AG) has been FDA-approved for individuals refusing other CRC screening methods, although it is not covered by Medicare due to its limited performance of approximately 70% sensitivity and 85% specificity [23,29].

Table 2.

Currently Available or Investigational Blood-Based Liquid Biopsy Tests for CRC Screening

Recently, a prospective, multicenter, cross-sectional observational study enrolled 48,995 asymptomatic adults aged 45–85 years at average risk for CRC who were willing to undergo screening colonoscopy (PREEMPT CRC cohort) [25]. The study evaluated the clinical performance of an investigational blood-based ctDNA test for CRC detection using colonoscopy with histopathology as the reference method. Test sensitivity for CRC was 79.2% (95% CI, 68.4%–86.9%) and specificity for advanced colorectal neoplasia (ACRN) was 91.5% (95% CI, 91.2%–91.9%). The negative predictive value for ACRN was 90.8% (95% CI, 90.7%–90.9%) and the positive predictive value for ACRN was 15.5% (95% CI, 14.2%–16.8%). All primary endpoints met the pre-specified acceptance criteria, except for the 12.5% sensitivity (95% CI, 11.3%–13.8%) for advanced precancerous lesions. Thus, liquid biopsy using ctDNA demonstrated acceptable accuracy for CRC detection in an average-risk population but showed limited sensitivity for advanced precancerous lesions.

A recent prospective ECLIPSE study assessed the performance characteristics of a cfDNA blood test in a population eligible for CRC screening [26]. The clinical validation cohort included 10,258 individuals, 7,861 of whom met the eligibility criteria and were evaluable in the final analysis. In total, 83.1% of the participants with CRC detected by colonoscopy had a positive cfDNA test, and 16.9% had a negative test, indicating a sensitivity of 83.1% (95% CI, 72.2%–90.3%). The sensitivity for stage I-III CRC was 87.5% (95% CI, 75.3%–94.1%), and the sensitivity for advanced precancerous lesions was 13.2% (95% CI, 11.3%–15.3%). Overall, 89.6% of the participants with no evidence of ACRN identified on colonoscopy had a negative cfDNA blood test, whereas 10.4% had a positive cfDNA blood test, resulting in a specificity for any ACRN of 89.6% (95% CI, 88.8%–90.3%). Therefore, cfDNA blood testing is promising for the detection of CRC; however, it is still limited in terms of its application for prevention and early intervention strategies. Based on this study, Shield (Guardant Health, Redwood City, CA, USA) became the first FDA-approved liquid biopsy as a primary option for CRC screening in average-risk adults aged 45 years and older and is covered by Medicare. Importantly, real-world data showed a high adherence rate of approximately 95%, supporting its feasibility for population-level CRC screening.

In recent years, cancer-specific exosomal cargos and products have gradually become the focus of cancer research. A Chinese study demonstrated the potential role of exosomes in CRC screening [27]. The study identified exosomes without enrichment or purification, based on the identification of the transmembrane protein CD147 on serum exosomes (exo-CD147) that are associated with CRC [27]. The levels of exo-CD147 were significantly higher in patients with CRC than in healthy controls. The AUC for exo-CD147 was 0.827 (95% CI, 0.764–0.891), outperforming conventional tumor markers, such as carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9), with AUCs of 0.630 (95% CI, 0.536–0.724) and 0.659 (95% CI, 0.559–0.759), respectively. Moreover, combining exo-CD147 with CEA further increased the AUC to 0.845 (95% CI, 0.784–0.908), and combining with CA19-9 increased the AUC to 0.832 (95% CI, 0.769–0.895). These findings suggest that exo-CD147 is a promising diagnostic biomarker for CRC. Typical cancer-associated mutational alterations can be detected at the messenger RNA level in serum exosomes from patients with CRC [31]. In a German study, exosomal quiescin sulfhydryl oxidase 1 (QSOX1) was identified as a promising biomarker for the early detection of CRC, with significantly lower expression in patients with CRC compared with control individuals [28]. In the AUC analysis, exosomal QSOX1 demonstrated an AUC of 0.904 (95% CI, 0.831–0.977) for overall CRC, 0.887 (95% CI, 0.785–0.988) for non-metastatic CRC, and 0.921 (95% CI, 0.843–0.999) for metastatic CRC compared with controls. Thus, research is being actively conducted on a diverse range of blood-based liquid biopsy biomarkers for CRC screening.

EVOLUTION OF LIQUID BIOPSY

Recent studies have focused on combining previously identified biomarkers to improve diagnostic performance. In a recent Chinese study, investigators evaluated a composite score based on plasma DNA methylation of SEPT9, syndecan 2 (SDC2), and branched-chain amino acid transaminase 1 (BCAT1), each of which has been described as a biomarker for CRC detection [32]. The composite score was derived from the cycle threshold values of the 3 methylated genes using a logistic regression model. SEPT9, SDC2, BCAT1, and their composite scores demonstrated strong discriminatory power between CRC patients and non-malignant controls. The composite score demonstrated an AUC of 0.929, with a sensitivity of 86.1% and a specificity of 97.6% for CRC detection. The composite score showed much lower cycle threshold values than the 3 individual biomarkers, indicating its superior utility for CRC detection. These findings indicate that a combined ctDNA methylation approach is more effective than using a single biomarker for CRC screening. Another Korean study also proposed a panel of exosomal microRNAs (miRNAs) to enhance the diagnostic accuracy of CRC over that of single miRNAs alone [33]. Four miRNAs were identified that discriminated patients with CRC from healthy controls: miRNA-23a, miRNA-486, miRNA-320a, and miRNA-125b. Individually, each miRNA demonstrated modest sensitivity for CRC detection, ranging from 53.3% to 80.0%. However, the combined miRNA panel substantially improved diagnostic accuracy, with 85.1% sensitivity for dual markers, 92.6% for triple markers, and 98.9% for quadruple markers. These findings underscore the potential value of exosomal multimarker panels for improving CRC screening performance.

AI technology has been integrated into liquid biopsies to improve the diagnostic accuracy of CRC screening. A Chinese study developed a blood-based cfDNA fragmentomics assay to differentiate CRC from AAs and non-cancerous colorectal diseases [34]. The investigators used 3 cfDNA features: copy number variation, arm-level fragment size distribution, and mutation context with mutational signatures. Six AI algorithms were applied to each cfDNA feature type to construct the final stacked model. In the training cohort, the optimal base models for each feature achieved AUCs ranging from 0.7800–0.9063. The final stacked model for CRC achieved an AUC of 0.9295 in the training cohort and 0.9258 in the validation cohort, with a sensitivity of 91.3% and specificity of 82.3% in the validation cohort. Notably, the model demonstrated exceptional accuracy in distinguishing AAs from benign cases, achieving an AUC of 0.846 and a sensitivity of 67.7%, outperforming traditional blood tests. This study highlights the advantages of cfDNA fragmentation based on AI technology for CRC screening. With continued technological advances and the integration of liquid biopsy with AI, diagnostic performance in this field is expected to improve further.

CHALLENGES OF LIQUID BIOPSY

A nested case-control study based on the Trøndelag Health study, which is one of the largest longitudinal population health studies, used a panel of 8 ctDNA markers for the detection of CRC [35]. An interesting finding of this study was that a positive panel was associated with an odds ratio of 4.59 (95% CI, 1.99–10.59) for being clinically diagnosed with CRC within the subsequent 24 months, with an AUC of 0.669. Since ctDNA markers for CRC can be detected through blood testing before clinical diagnosis, liquid biopsy can be regarded as evidence supporting the feasibility of early CRC screening. Despite this potential, substantial limitations of liquid biopsy preclude its adoption as a screening tool for CRC.

To date, no adequately powered randomized clinical trial has demonstrated that liquid biopsy–based screening reduces CRC-specific mortality. Without such data, causal inferences regarding screening benefits remain limited, and comparisons with established strategies such as FIT or colonoscopy are indirect. Evidence derived primarily from case-control or single-round prospective studies may not reflect outcomes in realworld validation studies, where participation patterns and colonoscopy capacity influence the overall effectiveness. Long-term adherence, repeated participation in multiple screening rounds, and diagnostic performance in real-world programs remain uncertain. Furthermore, the clinical outcomes of the limited number of validation studies are inconsistent. A prospective validation study of liquid biopsy enrolled 9,024 eligible participants and used ctDNA to detect multiple cancers in lung, liver, stomach, breast, and colorectum [36]. The sensitivity and specificity of this test for multi-cancer detection were 70.8% and 99.6%, respectively, which demonstrate the need for prospective validation of liquid biopsy for early cancer detection in population-based screening. Another large validation study enrolled more than 140,000 asymptomatic adults aged 50–77 years from the UK National Health Service to evaluate whether multi-cancer early detection using ctDNA analysis (the Galleri test) reduces the absolute number of late stage (III–IV) CRCs diagnosed after 3–4 years of follow-up. However, the preliminary results suggested a reduction in late-stage cancer diagnoses without statistical significance. Therefore, additional prospective validation studies are required to establish the clinical utility of liquid biopsies for CRC screening. In addition, detection rates of liquid biopsy for precancerous lesions are consistently lower, even though they show reasonable diagnostic performance for established CRC [25,26]. Specifically, for example, the sensitivity for AAs was 11% with the methylated SEPT9 assay in the PRESEPT study [23], 12.5% for advanced precancerous lesions with a ctDNA assay in the PREEMPT cohort [25], and 13.2% for advanced precancerous lesions with a cfDNA-based blood test in the ECLIPSE study [26]. Because the principal goal of screening is not only early detection but also prevention through the removal of precursor lesions, limited sensitivity for precancerous lesions may attenuate the potential for true mortality reduction.

In addition, liquid biopsies differ widely with respect to biomarker panels (e.g., methylation markers, mutation-based assays, and fragmentomics), analytical thresholds, and bioinformatics pipelines. This variability complicates cross-study comparisons, limits standardization, and constrains the validity of pooled analyses. Consequently, the interpretation of performance metrics across studies has remained inconsistent. Such heterogeneity complicates the robust validation of liquid biopsies as a screening modality for CRC. In addition to the heterogeneity of liquid biopsy platforms, their high costs remain a major barrier to their implementation in CRC screening. Although modeling studies suggest that improved adherence could offset higher per-test costs, robust real-world health-economic evaluations are lacking. The balance between test cost, positivity rate, downstream colonoscopy demand, and incremental life-years gained has not been clearly established. Finally, standardized management algorithms that involve downstream clinical pathways following a positive liquid biopsy result have not been fully defined. Questions persist regarding the optimal timing and prioritization of colonoscopy, management of false-positive results, communication of uncertain findings, and their integration with existing screening programs. Without clearly established clinical pathways, implementation at this scale may generate inefficiencies and unintended harm. Taken together, these limitations underscore that the role of liquid biopsies as a primary CRC screening modality requires further validation through rigorous trials, real-world implementation studies, and health system-level evaluations.

CONSIDERATIONS FOR ORGANIZED SCREENING

Moreover, several additional considerations must be addressed before liquid biopsy can be considered for organized CRC screening strategies. First, liquid biopsy platforms involve complex laboratory workflows, proprietary sequencing technologies, and bioinformatic pipelines. These factors contribute to substantial analytical and operational costs compared to established screening modalities, such as FIT or colonoscopy. Economic evaluations using decision-analytic and Markov models have consistently shown that colonoscopy remains the most cost-effective strategy under base-case assumptions, whereas blood-based assays are associated with higher overall costs [37]. Cost-effectiveness of blood-based testing may be highly sensitive to the test price, sensitivity for AAs, adherence rates, and downstream colonoscopy costs. Furthermore, limited insurance coverage and heterogeneous reimbursement policies may exacerbate disparities in access, particularly in publicly funded screening programs. Until robust evidence demonstrates competitive cost-effectiveness at this scale, liquid biopsy cannot be considered a screening tool in an organized CRC screening program. Second, most studies on liquid biopsy have been conducted in research-intensive health systems with advanced genomic infrastructure [36,38,39]. Implementation at the population level requires standardized processing, temperature-controlled logistics, centralized high-throughput sequencing facilities, secure bioinformatic pipelines, and integrated reporting systems. Variability in pre-analytical factors (e.g., blood collection tubes, processing time, and storage conditions), cfDNA extraction methods, sequencing depth, and variant-calling algorithms introduces heterogeneity across platforms and studies. This lack of harmonization limits scalability and poses challenges for quality assurance within an organized CRC screening program. Third, unlike the FIT, which benefits from well-established analytical thresholds and external quality assurance frameworks, liquid biopsy assays are not fully standardized across manufacturers. Differences in target regions, assay sensitivity thresholds, and bioinformatics filtering criteria affect the reproducibility and interlaboratory comparability [40,41]. Moreover, the absence of universally accepted reference standards for early-stage CRC or ACRN detection complicates performance benchmarking. In addition, robust external validation in asymptomatic average-risk populations is limited. Fourth, screening interventions must balance early detection with the risk of overdiagnosis. Liquid biopsy, which detects tumor-derived signals without clear anatomical localization, may identify indolent neoplasms or lesions of uncertain clinical significance. In multi-cancer early detection studies, false-positive signals result in additional extensive diagnostic workups, including imaging and invasive procedures [38]. False positives may lead to patient anxiety, unnecessary investigations, and increased healthcare utilization. Overdiagnosis is particularly concerning in organized screening programs, where large numbers of asymptomatic individuals are tested, and even small false-positive rates can translate into a substantial downstream burden. Finally, the effectiveness of CRC screening depends not only on test sensitivity and participation but also on timely access to diagnostic colonoscopy in the face of a positive result. Modeling studies have suggested that increases in positivity rates, even with modest specificity reductions, can substantially increase demand for colonoscopy [16]. If liquid biopsy demonstrates lower specificity or uncertain risk stratification for colorectal neoplasia, referral volumes may exceed the existing endoscopic capacity, especially in health systems already constrained by workforce and infrastructure limitations. This could delay diagnostic confirmation for true-positive cases and reduce the effectiveness of the overall program.

Compared with current stool-based modalities, FIT and stool DNA test, blood-based liquid biopsy offers practical advantages, including ease of sampling, high patient acceptability, and potential integration into routine clinical visits. In addition, multi-cancer detection platforms raise the possibility of broader oncologic applications beyond CRC. Therefore, liquid biopsy represents an emerging primary screening tool with substantial promise, but important limitations, such as limited sensitivity for AAs, uncertainty regarding long-term mortality reduction, assay heterogeneity, unclear downstream clinical pathways after positive results, and insufficient real-world cost-effectiveness data. An organized CRC screening is fundamentally a population-based public health intervention. Integration of blood-based liquid biopsy will require rigorous demonstration of clinical utility, cost-effectiveness, scalability, standardization, and sustainable colonoscopy capacity. At present, the evidence does not support the role of liquid biopsy in organized CRC screening programs, although it represents a promising technological advance.

CONCLUSIONS

Liquid biopsy offers practical advantages, including ease of sampling, high patient acceptability, and potential integration into routine clinical practice. In addition, multi-cancer detection platforms raise the possibility of broader oncologic applications beyond CRC. However, it also has important limitations, such as limited sensitivity for precancerous lesions, uncertainty regarding long-term mortality reduction, assay heterogeneity, unclear downstream clinical pathways after positive results, and insufficient cost-effectiveness data. Currently, liquid biopsy may be best positioned as a complementary strategy for individuals unwilling to undergo stool-based testing or colonoscopy rather than as a replacement for established modalities. Broader adoption as a primary CRC screening tool requires robust prospective validation, demonstration of mortality reduction, standardization of assay platforms, and integration into organized screening programs.

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