PSE is a patented technique that combines PSA with an extra epigenetic test, so far mainly for routine screening of people who *haven't* been diagnosed with prostate cancer yet.

It's still the same old PSA test at the core, but the company that promotes it has shown evidence that adding some epigenetic tests reduces the number of false positives for screening the general population (e.g. people who haven't been diagnosed with prostate cancer) — in other words, if someone comes back with a borderline PSA result, the "E" part (epigenetic) might be able to rule out the need for an MRI and biopsy, at least at that time.

They've claimed it's helpful in other situations as well, but I don't know if they've published any peer-reviewed studies to back that up yet.