Liquid Biopsy Captures Gene Activity Patterns in Small-Cell Lung Cancer

Small-cell lung cancer accounts for approximately 15% of lung cancer cases and is characterized by rapid growth and spread. Many patients are diagnosed at an advanced stage, and tumors often recur after initially responding to treatment. Monitoring disease progression through repeat tissue biopsies can be invasive and challenging for these patients. New findings suggest that blood-based testing may offer a less invasive way to track the disease and identify active biological programs driving tumor behavior.

Researchers at Hebrew University-Hadassah Medical School developed a blood-based approach to assess tumor burden and active biological programs in small-cell lung cancer. The method uses cell-free chromatin immunoprecipitation sequencing (cfChIP-seq) to analyze fragments released into the bloodstream by dying cells. These fragments contain DNA wrapped around histone proteins, whose chemical modifications can reveal which genes were active in the cells of origin.

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Unlike conventional liquid biopsies that focus on DNA sequence changes, cfChIP-seq examines patterns of gene activity. Researchers analyzed 441 plasma samples from patients with small-cell lung cancer, patients with other cancers, and healthy individuals. They also compared blood-based findings with gene activity in tumor tissue, using approximately one milliliter of plasma per test.

The analysis identified molecular signatures characteristic of small-cell lung cancer and enabled researchers to develop a quantitative score reflecting the strength of cancer-associated signals. This score correlated with tumor burden measured by imaging and changed in response to treatment. Median scores declined following treatment, consistent with reduced tumor mass, while higher scores were associated with shorter survival.

The blood-based analysis also revealed molecular signatures associated with different small-cell lung cancer subtypes, closely reflecting the activity of key genes in matched tumor tissue. Some samples showed overlapping signals from multiple subtypes, highlighting the biological complexity of the disease and the potential value of blood-based profiling for monitoring tumor activity.

The observational study, conducted with the U.S. National Cancer Institute, part of the National Institutes of Health, was published in the Journal of Clinical Investigation on October 1, 2026. The method is not yet ready to replace tissue biopsies or guide routine treatment decisions, and larger studies are needed to establish how reliably it tracks changes and whether using its results to choose treatments improves patient outcomes.

Related Links
Hebrew University-Hadassah Medical School
US National Cancer Institute