PSA Doubling Time  Last Modified: December 10, 2006  Share
article   Dear OncoLink "Ask The Experts,"  Can you please
explain PSA doubling time?    This is actually a fairly
difficult question. PSA doubling time is supposed to reflect
tumor growth, so the doubling time should reflect the time it
takes for the number of tumor cells to double. The
straightforward answer is that it is the time it takes for the
PSA to go from X to 2X. This is absolutely true after
prostatectomy, because there is no other source of PSA.  In a
patient who still has a prostate in place (i.e., after
radiation, brachytherapy, or hormone therapy) it is more
difficult to interpret this value because there are two sources
of PSA, the benign and malignant prostate tissue. However, the
tumor doubling time is affected by the contribution from
malignant portion only.  Imagine a situation where the baseline
PSA from a benign prostate is 3.6, and it rises to 4.0 because
of a new carcinoma (i.e. the contribution from the cancer is
0.4). For the