What happens if PSA levels start rising after surgery or radiation for prostate cancer? Up to a third of men treated for the disease will eventually confront this problem. If there's no accompanying evidence of cancer on imaging scans, then men have what's called a biochemical recurrence. This means that PSA - the biochemical marker in this case - is flagging the presence of cancer cells that doctors are still unable to see.

Biochemically recurring cancer is asymptomatic, and it can take years for visible metastases to appear. Sometimes men live the rest of their lives with a rising PSA without ever developing metastases.

Now, an ultra-sensitive scanning technology is raising new questions about biochemical recurrence and how to manage it.

Test results influence treatment decisions

This scan works by illuminating a protein on cancer cells called prostate-specific membrane antigen (PSMA). A PSMA scan can reveal small tumors in the body that older, conventional imaging technologies, such as bone scans or magnetic resonance imaging, are unable to detect.