Cancer Antigen 125

CA-125 (also known as MUC16) is a mucin-type glycoprotein with a molecular weight exceeding 200 kilodaltons. It is normally expressed at low levels on the surface of mesothelial cells lining the peritoneum, pleura, and pericardium, as well as on epithelial cells of the fallopian tubes, endometrium, and endocervix. In ovarian cancer, the gene encoding CA-125 is overexpressed, leading to markedly elevated levels of the protein in the bloodstream. A serum CA-125 level above 35 U/mL is conventionally considered elevated, though this threshold does not by itself confirm malignancy.

The clinical utility of CA-125 is strongest in the context of known ovarian cancer, where serial measurements are used to track treatment response during chemotherapy and to monitor for recurrence after primary treatment. A rising CA-125 level in a patient with a history of ovarian cancer may precede clinical or radiographic evidence of recurrence by several months. However, CA-125 has significant limitations as a screening tool: it is elevated in only about 50% of early-stage (stage I) ovarian cancers and can be increased by numerous benign conditions including endometriosis, pelvic inflammatory disease, liver cirrhosis, and even menstruation.

Despite these limitations, CA-125 remains one of the most widely ordered tumor markers in clinical oncology. Its value increases substantially when interpreted as a trend over time rather than as a single value, and when combined with imaging and other clinical data. Research into algorithms that analyze the rate of change in CA-125 levels — such as the Risk of Ovarian Cancer Algorithm (ROCA) — has shown that longitudinal interpretation may improve specificity for malignancy detection.

Prevena Health is exploring whether continuous CA-125 monitoring may enhance the clinical value of trend-based analysis. Research on algorithms like ROCA has demonstrated that the trajectory of CA-125 over time is more informative than any single measurement, but current clinical practice is limited to quarterly or semi-annual blood draws. Continuous surveillance through a wearable platform may provide the granular temporal data needed to detect subtle upward inflections earlier.

This approach may support both post-treatment recurrence monitoring for ovarian cancer patients and research into whether continuous CA-125 trend data can improve the specificity of longitudinal screening algorithms. Prevena's platform is designed to complement — not replace — existing clinical surveillance protocols and imaging-based assessments.