Prostate Cancer with Low PSA
One of the problems with screening tests for cancer is that
there is an assumption that if you have a negative test, you
don't have cancer. Many people just don't realise that you can
have cancer with a negative screening test. For prostate cancer
serum PSA levels of 4 μg/L or more are considered to show
the possible presence of cancer. An analysis of men in a large
randomised study shows that cancer is also found in men with
lower levels.
Although the risk of finding a cancer on biopsy is directly
related to PSA levels below 4 μg/L, there is no PSA value
below which a man has no risk of prostate cancer. Moreover, this
statement applies not just to any grade of prostate cancer, but
even to high grade cancers where disease progression in the
absence of treatment is to be expected.
Its importance is that it is a harsh reminder of the failures as
opposed to the benefits of screening. Older men with normal PSA
values of 4 μg/L or below should still be on the lookout
for warning signs, as 1 in 8 will have prostate cancer worth
treating despite that normal result.