The basic test measures blood levels of prostate specific Androgen or PSA. However, the standard PSA cannot distinguish between cancers that grow so slowly that they can safely be left alone, and aggressive life threatening tumors that call for surgery or radiation therapy.
The new test measures three different types of PSA. Combined with annual biopsies or tissue samples, it was about 70% accurate in singling out the aggressive tumors in a small study.
More research is needed but authors say it's exciting news.