Cancer Biomarkers: Advancements using blood-derived biospecimens

Cancer keeps challenging medical science, but recent years have brought real progress in how we detect, monitor, and treat it — a central focus of our oncology biospecimen portfolio. Blood-based sampling is central to this progress, opening new paths for finding and acting on cancer biomarkers. As care shifts toward minimally invasive, precision-guided approaches, blood-derived samples are taking center stage — plasma, serum, whole blood, peripheral blood mononuclear cells (PBMCs), and circulating tumor cells (CTCs).

Discovering Cancer Biomarkers in Blood Samples

Traditional cancer diagnosis often relies on tissue biopsies and imaging. These can be invasive and risky, and sometimes aren’t even possible, especially when a tumor sits deep inside the body or in a critical location. Blood holds unique promise instead. A simple draw makes it easy to access, and it gives a window into the body’s real-time molecular state.

A few key reasons are pushing cancer biomarker research toward blood-based samples:

• Minimal invasiveness: Lower risk and discomfort for patients.
• Dynamic insight: The ability to capture changes in tumor cells and their microenvironment during disease progression or treatment.
• Scalability: Enabling large-scale screening and monitoring across diverse populations.

Let’s look at how different blood-based samples help track, diagnose, and shape cancer care.

Whole Blood: The Raw Material

Analysis doesn’t always start with separated plasma or serum. Whole blood testing keeps all cell types, plasma, and serum just as they exist in the body. Researchers can run genomic, transcriptomic, and metabolomic assays directly from a drop or tube of whole blood, which makes it well suited for point-of-care diagnostics and comprehensive omics studies.

Whole blood is particularly useful for:

• Circulating cell analyses: Assessing the distribution of different white blood cells, which can shift in cancer and help predict prognosis.
• Host response profiling: Studying how the immune system responds to a tumor or to treatments such as immunotherapy.

Plasma vs. Serum: Nuances that Matter for Cancer Biomarkers

Plasma and serum may look similar, but their differences play a big role in discovering and characterizing cancer biomarkers.

Property	Plasma	Serum
Definition	Clear fluid remaining after centrifuging blood with anticoagulants	Clear fluid after blood coagulates and is centrifuged
Key Components	Water, proteins (including clotting factors), hormones, metabolites, cell-free nucleic acids (cfDNA/cfRNA)	Similar to plasma but without most clotting factors
Preparation	Requires anticoagulants (e.g., EDTA, heparin)	No anticoagulant; allows natural clotting to occur
Typical Uses	Liquid biopsy, circulating tumor DNA (ctDNA), proteomic studies, biomarker discovery	Serological tests, some metabolomic and protein biomarker research
Advantages	Reflects circulating markers in their native state, fewer background signals from clotting	Easier sample processing in some contexts, higher yield of certain proteins

Researchers often prefer plasma for cancer biomarker studies since it retains clotting factors and stays closer to the true biochemical makeup of circulating blood. Serum still has value for protein analyses where clotting-related factors don’t get in the way.

Plasma: A Dynamic Reservoir for Cancer Biomarker Discovery

The process is surprisingly simple: draw blood, add an anticoagulant, and spin it down. What’s left is plasma full of cell-free DNA, RNA, proteins, metabolites, and extracellular vesicles. Healthy cells release these molecules, and so do tumor cells — which is the foundation of the “liquid biopsy” revolution.

Key applications in oncology include:

• Circulating tumor DNA (ctDNA): Tumor cells shed small fragments of DNA into the bloodstream. Sensitive assays can detect mutations, amplifications, and methylation changes that guide therapy and reveal resistance.
• Cell-free RNA (cfRNA): Offers clues about gene expression, splicing variants, and tumor heterogeneity.
• Protein biomarker panels: Large multiplex screens are starting to reveal early warning signals for various cancers, often before symptoms arise or imaging detects a mass.

By sampling plasma repeatedly over time, clinicians can track tumor evolution, monitor treatment response, and spot signs of relapse months ahead of conventional approaches.

Serum: Unlocking Insights into Cancer Biomarkers

Serum is missing certain molecules that plasma has, but it makes up for that with well-established workflows and deep historical datasets. Diagnostic tests for cancer antigens — like PSA for prostate cancer, CA-125 for ovarian cancer, or CEA for colon cancer — often use serum.

Some studies find serum better for detecting high-abundance proteins, autoantibodies, or metabolic profiles linked to cancer risk. The clotting process may even expose, or “unmask,” antigenic proteins that would otherwise stay hidden in plasma.

Peripheral Blood Mononuclear Cells (PBMCs): Unveiling the Immune Landscape

Extracted from whole blood via a density gradient, PBMCs include lymphocytes (T cells, B cells, natural killer cells) and monocytes. Studying them sheds light on:

• Immune surveillance: The ability (or failure) of the immune system to detect and destroy tumor cells.
• Immunotherapy response: Identifying cellular markers that predict success with emerging treatments.
• Tumor-immune interaction: Untangling immune profiles that distinguish aggressive cancers from more benign forms.

Single-cell sequencing and advanced flow cytometry now let researchers map immune cell states and functions in fine detail, from a simple blood sample.

Circulating Tumor Cells (CTCs): Cancer’s Messengers

One of the most exciting developments is capturing and characterizing circulating tumor cells. These rare cells, shed by tumors, travel through the bloodstream and sometimes seed distant metastases.

Detecting and studying CTCs isn’t easy. Ordinary blood cells vastly outnumber them, so scientists need intricate enrichment techniques, often based on unique surface markers or physical properties. Once isolated, CTCs offer a lot of information, including:

• Tumor genotype and phenotype: Analysis of mutations, gene expression, protein markers, and drug sensitivity.
• Metastatic potential: Certain features on CTCs may signal how likely the cancer is to spread or recur.
• Real-time monitoring: Sequential counts and analysis over time help refine treatment decisions.

Since CTCs are viable tumor cells, they give direct evidence of ongoing disease activity. They may even work as “avatars” for testing potential therapies outside the body.

Current Challenges and Points of Progress

Blood-based cancer biomarkers generate a lot of enthusiasm, but reality brings some technical and biological complications:

• Sensitivity and specificity: Detecting mutations or rare cells with high confidence is hard amid overwhelming signals from normal blood constituents.
• Standardization: Variability in sample handling, processing, and analytical platforms can hurt reproducibility and slow clinical adoption.
• Integration: Combining information from plasma, serum, PBMCs, and CTCs into one coherent, actionable profile is both a computational and a logistical challenge.

Even so, advances in molecular biology, digital PCR, next-generation sequencing, and bioinformatics are closing these gaps. Hospitals and diagnostic labs increasingly use algorithms that combine signals from multiple blood-based tests to guide patient care.

Emerging Frontiers: Multi-Analyte Testing

The future likely won’t depend on a single biomarker or blood component. The next step forward pairs diverse analytes into precision algorithms, improving early cancer detection, characterization, and personalized therapy. Projects underway gather plasma DNA, serum proteins, CTC counts, and immune cell profiles to build “digital twins” of each patient, mapping their biology in unprecedented detail.

Picture screening tests that flag cancer in its earliest stages, routine blood tests that track microscopic disease, and treatment plans that update dynamically based on real-time molecular signals. This multi-analyte vision points toward more reliable, comprehensive cancer care — moving away from one-size-fits-all and toward truly personalized medicine.

Increasing Participation and Impact

One underappreciated benefit is how this approach improves patient engagement. Blood draws feel far less daunting than surgical biopsies or repeated imaging. That means more frequent sampling, better disease tracking, and more willingness among at-risk or monitored people to join screening and monitoring programs.

Large, population-level research studies benefit too. Blood sampling helps researchers build richer biobanks, which speeds up the discovery, validation, and translation of new biomarkers into everyday clinical practice.

A New Era in Cancer Diagnostics

The combination of blood-based sampling, advanced molecular assays, and data science is steadily reshaping oncology. These methods don’t just promise earlier detection, better risk stratification, and closer monitoring — they also give us a deeper, more personal understanding of cancer biology.

Whether through plasma’s cell-free DNA, the protein-rich world of serum, the immune insight from PBMCs, or rare clues from CTCs, blood samples are reshaping every phase of the cancer journey.

The outlook for cancer biomarker research has never looked brighter. Blood, once just a passive witness to disease, now sits at the center of a revolution in how we find, understand, and beat cancer. Explore our full oncology biospecimen portfolio for related sample types and cancer research support.

Cancer Biomarker Reviews

There are many reviews on cancer biomarkers. Here are a few open access publications:

Cancer Biomarkers – Emerging Trends and Clinical Implications for Personalized Treatment

Circulating Tumor DNA to Monitor Treatment Response in Solid Tumors and Advance Precision Oncology

Liquid Biopsy in Cancer: Current Status, Challenges, and Future Prospects

Emerging Biomarkers for Non-Invasive Diagnosis and Treatment of Cancer: A Systematic Review

Discover Sanguine’s Oncology Biospecimen Portfolio and Blood-derived Oncology Samples

Sanguine supplies research-grade human PBMCs for studies like this.