Medical science has devised a promising new means of hunting for prostate cancer cells in the blood. It’s called molecular staging because the techniques it uses come from the high-tech field of molecular biology.
There are several ideas at work here. One is that PSA is only made by prostate cells. (This is not entirely true; PSA is also manufactured in tiny amounts at other body sites such as the urethral glands and submandibular gland.) Another is that PSA-secreting cells can be identified in the blood using a state-of-the-art technique called Polymerase Chain Reaction, or PCR. (PCR is an extremely powerful means of amplifying DNA—it works like a tiny, molecular Xerox machine, churning out countless copies of bits of genetic material.)
Before we discuss this new test, we must say that this technique should not be confused with simpler PSA measurements. It’s a different kettle of fish altogether! Other PSA tests, which we’ve discussed extensively in this chapter, determine how much PSA is circulating in the plasma, the liquid part of blood.
In the molecular staging technique, scientists extract cells from the blood to determine whether those cells can make PSA.
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