For decades, the “holy grail” of oncology has been the ability to detect cancer long before a patient feels a single symptom or a radiologist spots a mass on a scan. In the world of internal medicine, we know that time is the most critical variable; the earlier a malignancy is identified, the higher the probability of a successful cure. Today, we are seeing the emergence of a transformative technology known as “liquid biopsies”—blood tests designed to identify the molecular signatures of cancer circulating in the bloodstream.
These early detection blood tests for cancer do not look for the tumor itself, but rather for fragments of circulating tumor DNA (ctDNA) or specific protein markers that cancer cells shed into the plasma. While traditional screening—such as mammograms or colonoscopies—targets specific organs, a new generation of Multi-Cancer Early Detection (MCED) tests aims to screen for dozens of different cancer types from a single vial of blood.
As a physician and journalist, I have followed these developments with a mixture of professional excitement and clinical caution. While the data from recent large-scale studies are promising, it is essential to distinguish between a “signal” in the blood and a confirmed diagnosis. The transition from laboratory success to bedside application requires rigorous validation to ensure we are saving lives without subjecting healthy people to unnecessary, invasive follow-up procedures.
The Rise of Liquid Biopsies in Early Cancer Detection
The fundamental science behind these tests relies on the fact that cancer cells are often unstable. As they grow and die, they release fragments of their genetic material into the blood. Historically, medical consensus suggested that these fragments only appeared in advanced stages of the disease. However, recent research has proven that ctDNA is present even in the earliest stages, often before a tumor is large enough to be detected by conventional imaging.
By analyzing these fragments, clinicians can potentially identify the presence of cancer and, in some cases, pinpoint the “tissue of origin” (TOO). This allows doctors to move directly to the correct diagnostic tool—such as a specific biopsy or targeted scan—rather than searching blindly through the body. This shift from reactive medicine to proactive screening could fundamentally alter the trajectory of cancer care globally.
Analyzing the Galleri Test: A Step Toward the ‘Holy Grail’
One of the most discussed innovations in this field is the Galleri test, developed by the American biotech company Grail. This test is designed to screen for more than 50 types of cancer. The scale of its validation is significant; a large study involving 23,000 participants in the United States and Canada demonstrated that the test could identify signals of cancer in 216 individuals via VRT NWS.
The accuracy of the Galleri test is particularly noteworthy in its ability to avoid “false alarms.” In the same study, 61.6 percent of those who received a positive signal were effectively diagnosed with cancer within a year, and the test correctly excluded cancer in 99.6 percent of cases via VRT NWS. This high level of specificity is crucial as a low-specificity test would lead to an overwhelming number of healthy patients undergoing stressful and unnecessary medical interventions.
Despite these results, experts urge a balanced perspective. Filip Lardon, a cancer researcher at UAntwerpen, describes the results as a “hopeful step,” but cautions that “we are not there yet” via VRT NWS. The challenge remains in ensuring these tests are integrated into a broader clinical framework rather than used as standalone diagnostic tools.
AI-Driven Screening: The Role of OncoSeek
Parallel to the efforts of Grail, other platforms are integrating artificial intelligence and big data to refine detection. The OncoSeek blood test utilizes a combination of seven specific plasma tumor markers and a multivariable algorithm to calculate a Cancer Risk Score (CRS) and trace the tissue of origin via Kanker-Actueel.
The validity of OncoSeek has been supported by a large-scale study published in The Lancet, which tracked 7,565 participants between November 2012 and May 2022 via Kanker-Actueel. By moving away from single-threshold markers—which often result in high false-positive rates—and instead using AI to analyze multiple markers simultaneously, the test aims for a more precise screening process.
OncoSeek is CE-certified and has been made available through platforms in the Netherlands and Bulgaria, illustrating a move toward making this technology accessible outside of traditional high-cost clinical trials via Kanker-Actueel.
Beyond Detection: Monitoring Treatment with DELFI-TF
While much of the public focus is on early detection, liquid biopsies are equally revolutionary for patients already fighting the disease. The focus here shifts from screening to monitoring. A prime example is the DELFI-TF test, a collaboration between the Netherlands Cancer Institute (NKI), Johns Hopkins University, and DELFI Diagnostics via AVL.
The DELFI-TF test analyzes ctDNA to determine if a specific cancer treatment is working. In a study of 174 patients with metastatic colorectal cancer (part of the CAIRO5 phase III clinical trial), the test showed it could measure the effectiveness of therapy more accurately than traditional CT scans via AVL.
This is a significant quality-of-life improvement for patients. Instead of frequent, time-consuming hospital visits for CT scans, patients could potentially monitor their treatment progress via a simple blood draw at their GP’s office or even from home via AVL.
The Medical Reality: Hope vs. Hype
As we integrate these technologies, we must address the “what it means” for the average person. A positive result from an MCED test is not a diagnosis of cancer; it is a “signal” that requires further investigation. The danger of over-screening is the risk of over-diagnosis—finding small, slow-growing tumors that might never have caused harm in the patient’s lifetime, yet lead to aggressive treatments with significant side effects.
these tests are not replacements for established screenings. A blood test does not replace a colonoscopy or a mammogram; rather, it acts as a complementary layer of defense. The goal is to catch the cancers that traditional screenings miss, such as pancreatic or ovarian cancers, which often lack effective early-screening protocols.
Key Takeaways: Understanding Modern Cancer Blood Tests
- Multi-Cancer Early Detection (MCED): Tests like Galleri aim to find multiple cancer types (50+) before symptoms appear.
- Specificity Matters: High specificity (e.g., 99.6% for Galleri) reduces false positives, preventing unnecessary anxiety and procedures.
- AI Integration: Platforms like OncoSeek use AI and big data to analyze multiple plasma markers for higher accuracy.
- Treatment Monitoring: Tests like DELFI-TF use ctDNA to track therapy success, potentially replacing some CT scans for metastatic patients.
- Complementary, Not Replacement: These tests are intended to work alongside, not instead of, traditional screening methods.
The path forward involves larger, more diverse longitudinal studies to prove that early detection via blood tests actually leads to lower mortality rates. We have the tools to see the “whispers” of cancer in the blood; the next step is ensuring we interpret those whispers with absolute clinical precision.
Medical professionals and regulatory bodies continue to evaluate the long-term impact of these screenings. Further data from ongoing clinical trials will be essential in determining how these tests are integrated into national healthcare guidelines.
Do you believe liquid biopsies will eventually replace traditional screenings, or should they remain a secondary tool? Share your thoughts in the comments below.