One Step Ahead: Blood Test Detects Cancer 3 Years Before Symptoms Appear

Scientists have discovered that it is possible to detect signs of cancer in the blood up to three years before the disease shows symptoms. Using an advanced blood test called MCED, they have found small mutations in the DNA released by tumors long before a diagnosis. This paves the way for identifying cancer earlier and increasing the chances of treatment and cure.

Scientists are developing increasingly accurate ways to identify cancer even before a person has any symptoms or the disease is visible on traditional tests. A recent study has shown that this is already possible in some cases.

Researchers at Johns Hopkins Medicine analyzed blood samples from people who participated in a large study of cardiovascular disease called ARIC (Atherosclerosis Risk in Communities).

They chose 26 people who were later diagnosed with cancer and compared them with 26 healthy people who were similar in age and other characteristics. The goal was to find out if signs of cancer were already present in these people’s blood before diagnosis.

The test used in the study is called MCED, which stands for Multi-Cancer Early Detection. It is done using a simple blood sample, which is a test that looks a lot like what people do in labs to measure cholesterol, glucose, or other things in the blood.

But what this test looks for is much more specific: it looks for small pieces of circulating tumor DNA, which are fragments of genetic material released by cancer cells into the bloodstream.

When tumor cells begin to multiply, some of them die and release this DNA into the blood. The MCED test is able to “hunt” these small pieces of DNA and identify whether there are genetic changes or mutations that are characteristic of cancer cells.

Cancer cell dying

To achieve this, scientists use highly advanced genetic sequencing technologies. Imagine a machine that can “read” the letters of our DNA (A, T, C, G, which are the genetic codes) and compare them with the expected normal DNA. The device looks for errors or changes in this code that are typical of cancer.

High-precision equipment called next-generation sequencers (NGS) is used, which are capable of analyzing billions of pieces of DNA in a single blood sample.

Next-Generation Sequencing Machine

But because circulating tumor DNA appears in very small quantities, especially when the cancer is still in its early stages, the test needs to be extremely sensitive. That's why, in addition to sequencers, laboratories use sophisticated bioinformatics programs (software that analyzes genetic data) to detect even the smallest changes among millions of pieces of healthy DNA.

The most impressive thing was that, in four of these cases, the mutations were already there in blood samples collected more than three years before the official diagnosis.

To give you an idea, in the study, when scientists analyzed blood collected years before diagnosis, the tumor DNA was in concentrations 8 to 79 times lower than in the sample closest to the time the cancer was discovered. This shows the power of the test to identify something so tiny and early. It indicates that the cancer can be present and growing silently for years before causing symptoms.

The researchers highlighted that this discovery opens a new window of opportunity to identify and treat cancer at very early stages, when there is a greater chance of a cure.

They emphasize that this line of research could change the way we screen for the disease, allowing interventions long before the cancer has spread or become more difficult to treat.

The cancers identified with the multi-cancer early detection (MCED) test were mainly solid cancers, since these release more tumor genetic material (circulating tumor DNA, or ctDNA) into the bloodstream.

Although the study was small (26 people who developed cancer), the types of cancer detected included: lung cancer, pancreatic cancer, bowel cancer (colorectal cancer), ovarian cancer, and liver cancer.

These types were mentioned because they are known to release detectable mutations in the blood and are often difficult to diagnose early using traditional methods.

However, they also warn that there is still a need to study what to do after a positive test, to avoid unnecessary treatments and offer the best options to each patient. These advances show how science is trying to make diagnosing and fighting cancer earlier, more accurate, and less invasive.

READ MORE:

Detection of cancers three years prior to diagnosis using plasma cell-free DNA 

Yuxuan Wang, Corinne E. Joshu, Samuel D. Curtis, Christopher Douville, Vernon A. Burk, Meng Ru, Maria Popoli, Janine Ptak, Lisa Dobbyn, Natalie Silliman, Josef Coresh, Eric Boerwinkle, Anna Prizment, Chetan Bettegowda, Kenneth W. Kinzler, Nickolas Papadopoulos, Elizabeth A. Platz, and Bert Vogelstein 

Cancer Discov (2025)

https://doi.org/10.1158/2159-8290.CD-25-0375

Abstract:

To explore how early can cancers be detected prior to clinical signs or symptoms, we assessed prospectively collected serial plasma samples from the Atherosclerosis Risk in Communities (ARIC) study, including 26 participants diagnosed with cancer and 26 matched controls. At the index time point, eight of these 52 participants scored positively with a multicancer early detection (MCED) test. All eight participants were diagnosed with cancer within 4 months after blood collection. In six of these 8 participants, we were able to assess an earlier plasma sample collected 3.1 to 3.5 years prior to clinical diagnosis. In four of these six participants, the same mutations detected by the MCED test could be identified, but at 8.6 to 79-fold lower mutant allele fractions. These results demonstrate that it is possible to detect circulating tumor DNA more than three years prior to clinical diagnosis, and provide benchmark sensitivities required for this purpose.