Liquid Biopsies in Cancer: Technologies, Applications, and Emerging Advances

Liquid biopsies involve the minimally invasive collection and analysis of biofluids to detect disease-associated markers. Compared with tissue biopsies, they enable repeated sampling, providing real-time insights into a patient’s disease. In this infographic, we explore key technologies and emerging advances shaping the role of liquid biopsies in cancer diagnosis and monitoring. What are liquid biopsies? Tissue biopsy Liquid biopsy Invasive Single timepoint snapshot Limited sampling region Challenging to repeat May miss heterogeneity Time-consuming Minimally invasive Longitudinal monitoring Can capture systemic tumor signals Easily repeatable May better reflect tumor heterogeneity Potentially faster turnaround times The ctDNA liquid biopsy workflow Liquid biopsy workflows involve multiple steps and vary depending on the analyte. Clinical applications of liquid biopsies Liquid biopsies could help to inform several aspects of cancer management. Current challenges and limitations Despite offering advantages over tissue biopsies, liquid biopsies still face limitations. Emerging technologies and advances Technological advances are helping to address limitations and increase the clinical utility of liquid biopsies. ctDNA is widely used as it: • Is detectable across many cancer types • Supports mutation profiling and disease monitoring • Is compatible with PCR and nextgeneration sequencing (NGS) workflows Why standardization matters Pre-analytical variables can significantly influence liquid biopsy results. Factors to consider include sample collection, processing time, storage conditions, temperature, and freeze-thaw cycles. Liquid biopsy workflow for ctDNA: 1. Sample collection The sample is collected from the patient. 2. Isolation Plasma is isolated from whole blood by centrifugation. 3. ctDNA extraction Methods include silica-based membranes, magnetic beads, or phenol-chloroform extraction. 4. Detection and quantification Quantification is used to assess sample quality and estimate ctDNA abundance. ctDNA can be detected using PCR or NGS methods. PCR-based approaches detect known mutations and include variations such as dPCR, COLD-PCR, and BEAMing, while NGS approaches can detect a broader range of mutations and can use targeted or untargeted panels. 5. Bioinformatics analysis Data is analyzed and interpreted. 6. Clinical decision‑making Results inform cancer management. Diagnosis • Profile tumors at initial diagnosis • Multi-cancer early detection assays Treatment selection • Identification of actionable variants • Precision oncology Monitoring response • Tracking tumor burden • Real-time assessment of efficacy Minimal residual disease (MRD) detection • Detection of residual disease • Earlier identification of relapse Resistance monitoring • Emergence of resistance • Adaptive treatment strategies Sensitivity • ctDNA may represent less than 0.01% of total cfDNA in some patients • Particularly challenging in early-stage disease • Can result in false-negatives Operational • Long turnaround times • Complex workflows • Cost considerations Standardization • Limited harmonization between laboratories • Lack of reproducibility across platforms Specificity • Distinguishing true tumor signals from non-tumor DNA • Risk of false-positive findings Sample quality • Variable pre-analytical handling • DNA degradation during sample processing Future directions Liquid biopsies are expected to become an increasingly important component of precision oncology. Routine MRD-guided treatment decisions Population-scale multi-cancer early detection screening AI-assisted liquid biopsy dataset interpretation Integrated multiomic profiling from a single blood draw Greater adoption of non-blood liquid biopsy approaches Sponsored by Liquid biopsy samples can be sourced from several biofluids, including: • Blood • Saliva • Urine • Cerebrospinal fluid • Pleural effusion A range of analytes can be detected, including: • Circulating tumor DNA (ctDNA) • Circulating tumor cells • Extracellular vesicles • Non-coding RNAs Several molecular features can be analyzed, including: • Single nucleotide polymorphisms • Copy number variations • Insertions and deletions • Gene fusions and translocations • DNA methylation Ultra-sensitive sequencing Improved sequencing approaches can detect rare tumor-derived variants present at low frequencies. • Duplex sequencing • Error-corrected sequencing • Improved sensitivity in early-stage disease • More reliable MRD detection Analysis of cfDNA fragmentation patterns provides information beyond DNA sequence alone. • Fragment size profiling and endpattern analysis • Long-read sequencing approaches • Improved cancer detection • Better tissue-of-origin identification Fragmentomics DNA methylation signatures can reveal ctDNA tissue sources and may enable earlier cancer detection. • Genome-wide methylation profiling • Bisulfite-free methylation methods • Integration with other ctDNA analyses • Improved tissue-of-origin determination • Enhanced sensitivity for early-stage cancers Methylation-based assays Combining multiple biological signals can provide a more comprehensive view of disease. • Integration of genomics, epigenomics, transcriptomics, proteomics, and fragmentomics • Increased diagnostic sensitivity • Improved disease monitoring Multiomic liquid biopsies Researchers are increasingly expanding liquid biopsy approaches to use alternative biofluids for different cancers. • Urine • Cerebrospinal fluid • Saliva • Improved access to tumor-specific signals • Expanded clinical applications Beyond blood Advanced computational methods are helping extract clinically meaningful signals from complex liquid biopsy datasets. • Pattern recognition across complex datasets • Noise reduction and signal enhancement • Predictive classification models • Improved cancer detection accuracy • Personalized patient monitoring AI and machine learning Future developments may include: Liquid Biopsies in Cancer: Technologies, Applications, and Emerging Advances By Anna MacDonald | Designed by Janette Lee-Latour While liquid biopsies are increasingly being used in other disease areas, their primary use is in cancer.