USC Tries Blood Test to Spot Breast Cancer Early

A new Phase I study at the USC Norris Comprehensive Cancer Center is testing whether a liquid biopsy can spot breast cancer before mammography detects it. The trial will enroll patients who will provide two blood samples a year apart, and the results will be compared to standard imaging and biopsy outcomes to see if the test picks up disease earlier.

Trial design and aims

The design involves drawing blood at two time points and then matching those findings against the patients’ diagnostic results. This 12‑month interval allows researchers to see whether the test detects cancer before conventional methods flag it. By tracking changes over a year, the study can also assess how early the blood markers appear relative to mammogram findings.

Instead of searching for tumor DNA, the assay looks for rare cancer cells and large extracellular vesicles—tiny packages released by tumor cells that travel in the bloodstream. These markers may appear even when tumors are still small and invisible on imaging. Identifying them could give doctors a signal of early cancer activity that current tests miss.

Currently, mammography can miss early cancers and often triggers extra scans, biopsies, or months of waiting, which heighten patient anxiety and delay treatment. A reliable blood test could reduce those gaps and give clinicians more information when the disease is still most treatable, according to the study leaders.

If Phase I shows promise, investigators plan a larger Phase II trial. The same technique might later be adapted to screen for other solid tumors such as colon or lung cancer.