This is NOT about a new blood test for prostate cancer screening.   PSA
(prostate specific antigen) is a subtance produced by prostate cells.
Prostate cancer cells when they proliferate may produce increased
amounts of PSA, some of which escapes into the blood.   But other things
than prostate cancer can also increase PSA levels.   And some cancers
don't produce excess PSA.  PSA testing has been used to screen for
prostate cancer for at least 15 years.  A high PSA test would lead to a
biopsy which may then show the existence of prostate cancer.  Depending
on a variety of factors including the health and life expectancy of the
patients, more or less aggressive forms of treatment,  or no treatment
at all, might be advised for the patient.  During this time there has
been ongoing considerable controversy about whether such screening is
justified.  Supporters say that it can catch prostate cancer before it
metastasizes and it can thus be cured.  Opponents say it is not reliable
enough.  They also say that many cases of prostate cancer need never be
treated because they grow very slowly and may never affect the patient
during his lifetime.  Treatment has side effects, so it is not without
cost.  Many studies have been done, some supporting screening through
PSA testing, and other purportedly showing it is not an effective use of
resources.   The article refers to a study which claims to show that PSA
screening results in at least a 35 percent reduction in the incidence of
metastatic prostate cancer,  so it would be in the first category.