Cancer Antigen (CA) 15-3 details

CA 15-3 is a tumor marker used mainly to help monitor treatment response and detect recurrence in people already diagnosed with breast cancer. Like similar tumor markers (CA 27-29), it isn't used to screen for or diagnose breast cancer in the general population, since it isn't sensitive or specific enough on its own — many early-stage breast cancers don't raise CA 15-3 at all, and non-cancerous conditions (like liver disease or benign breast conditions) can occasionally elevate it too. Its main clinical value comes from tracking the trend over time in someone with a known diagnosis, where a rising level can prompt further evaluation for recurrence or progression.