Simple Blood Test Detects Cancer in Patients with Non-Specific Symptoms

These symptoms can be caused by cancer, other serious diseases, or benign conditions, making it difficult to decide who should undergo extensive testing. Current diagnostic pathways may delay cancer detection or expose patients without cancer to unnecessary investigations. Researchers have now shown that a blood-based protein signature can help distinguish cancer from other conditions at an early stage, offering a potential tool to guide clinical prioritization.

In research led by Karolinska Institutet (Stockholm, Sweden), in collaboration with Danderyd Hospital (Stockholm, Sweden), investigators explored whether proteins circulating in blood plasma could provide early clues to cancer before standard diagnostic workups begin. They used large-scale proteomics, a technology that allows simultaneous measurement of thousands of proteins from small blood volumes.

Blood samples were collected from nearly 700 patients referred to diagnostic centers before any imaging or invasive diagnostic procedures were performed. Using proteomic analysis, levels of 1,463 different plasma proteins were measured in each patient. From this dataset, the researchers identified a specific combination of proteins, referred to as a protein signature, that was strongly associated with a subsequent cancer diagnosis.

Based on the protein signature, the team developed a predictive model capable of distinguishing cancer patients from those with other serious conditions, including inflammatory, autoimmune, and infectious diseases. Importantly, many of the non-cancer patients had illnesses that produce symptoms similar to cancer, closely reflecting real-world clinical scenarios. The results, published in Nature Communications, demonstrated high precision in separating cancer from non-cancer cases, supporting the clinical relevance of the approach.

The researchers stress that the blood test is not intended to replace imaging diagnostics or biopsies. Instead, it could function as a decision-support tool to help clinicians prioritize patients for further testing, such as PET-CT scans, while reducing unnecessary investigations in low-risk individuals. Next steps include evaluating the method in primary care settings, where cancer prevalence is lower, to assess its performance and feasibility before broader clinical adoption.

“The study shows the potential of large-scale proteomics for extracting clinically relevant information from small amounts of blood,” said associate professor Mikael Åberg.

Related Links:
Karolinska Institutet
Danderyd Hospital