Breast cancer is one of the most common cancers affecting women around the world.
Thanks to better screening, surgery, chemotherapy, and newer medicines, many patients now survive much longer than in the past. However, one of the biggest fears after treatment is that the cancer may come back.
Doctors usually monitor patients after treatment using scans, physical exams, and by watching for symptoms. The problem is that cancer recurrence is often only discovered after tumors have grown large enough to appear on imaging tests or start causing health problems. By that stage, the disease may already have spread.
Now, researchers from Lund University in Sweden have developed a new blood test that may change how breast cancer is monitored in the future.
The scientists created a method called Pathlight, which can detect tiny traces of tumor DNA in the bloodstream long before cancer becomes visible on scans or causes symptoms. Their findings were published in the journal EMBO Molecular Medicine.
The researchers say the new test may help doctors identify recurrence much earlier than current methods, giving patients a better chance of receiving treatment sooner.
Cancer cells release small fragments of DNA into the blood. This is known as circulating tumor DNA. Detecting these tiny fragments is extremely difficult because they exist in very small amounts, especially after treatment when only a few cancer cells may remain.
The Lund University team designed Pathlight to look for the unique genetic fingerprint of each patient’s tumor. Every cancer develops its own specific genetic changes, and the new blood test tracks those exact changes in the bloodstream.
Professor Lao Saal, senior author of the study and researcher at Lund University, explained that the technology can measure very small amounts of tumor DNA with high precision.
According to the researchers, this allows doctors to detect signs of cancer activity even before tumors can be seen using modern imaging technology.
The study involved 136 breast cancer patients who received chemotherapy and surgery for different forms of breast cancer.
Researchers collected blood samples at several stages of treatment. Samples were taken at diagnosis, during chemotherapy, shortly after surgery, and regularly during follow-up care for as long as six years.
The results were striking.
Among patients who later developed metastatic breast cancer, the blood test detected signs of recurrence a median of 13.8 months before the disease became clinically visible.
In some patients, the test detected cancer activity almost four years earlier than existing medical methods.
This means doctors could potentially identify returning cancer far sooner than they can today.
The study also found that tumor DNA was detectable in nearly 90% of patients before treatment began.
In about 21% of patients, tumor DNA was still detectable after chemotherapy given before surgery. Researchers believe this may indicate that treatment was not fully successful in removing all cancer cells.
Another important finding involved treatment response.
In roughly 13% of patients, tumor DNA levels did not clearly decline during treatment. These patients had a much higher risk of later recurrence.
The researchers said this suggests the blood test may help doctors quickly identify patients whose cancer is not responding well to chemotherapy.
Currently, doctors often use a measurement called pathological complete response, or pCR, to judge treatment success before surgery. This means no visible cancer cells remain after chemotherapy.
However, the new blood test appeared to provide even more accurate information about future recurrence risk than pCR.
The researchers believe this could eventually help personalize treatment decisions.
For example, patients at high risk of recurrence might receive stronger or additional treatments earlier. At the same time, patients at very low risk may be able to avoid overly aggressive therapies and unnecessary side effects.
Niklas Loman, senior oncologist at Skåne University Hospital and one of the study researchers, said the findings may help improve both cancer treatment and long-term patient care in the future.
He explained that the technology may allow doctors to better identify which patients truly need intensive treatment and which patients could safely receive less aggressive care.
The researchers also highlighted practical advantages of the new system.
Some advanced genetic testing methods can provide more detailed information, but they are often expensive, time-consuming, and difficult to use routinely in large numbers of patients.
Pathlight was designed to be faster and more cost-effective while still maintaining strong accuracy.
Even so, scientists say more research is still needed before the blood test becomes part of standard medical care.
The study involved a relatively limited number of patients, and larger clinical trials will be needed to confirm the findings across broader populations.
Researchers also need to determine how doctors should respond when the blood test detects recurrence early. For example, it is still unclear whether earlier treatment based on tumor DNA detection will improve long-term survival.
Despite these unanswered questions, many experts believe blood-based cancer monitoring represents an important future direction in oncology.
Liquid biopsies, which analyze blood samples instead of traditional tissue biopsies, are becoming increasingly important because they are less invasive and easier to repeat over time.
The Lund University study adds to growing evidence that blood tests may eventually allow doctors to monitor cancer more precisely, detect recurrence earlier, and personalize treatment more effectively.
Overall, the findings are highly promising because they show that tiny traces of cancer may be detectable long before tumors appear on scans. Detecting recurrence more than a year earlier could potentially give doctors and patients valuable extra time for treatment decisions.
However, caution is still necessary because the technology has not yet been tested in large real-world clinical settings. Researchers still need to prove that earlier detection using this blood test actually improves survival and patient outcomes. Even so, the study represents an exciting step toward more personalized and proactive cancer care in the future.
Source: Lund University.
