Monday, 21 February 2011

Below is an extract from Dr. Patrick Walsh’s Guide to Surviving Prostate Cancer
It is a very useful book, before, during and post treatment; available from Amazon.

PSA Anxiety:
The Downside of Ultra- Sensitive PSA Tests

You've had the radical prostatectomy, but deep down, you're terrified that it didn't work. So here you are, a grown man, living in fear of a simple blood test, scared to death that the PSA- an enzyme made only by prostate cells, but all of your prostate cells are supposed to be gone - will come back. Six months ago, the number was 0.01. This time, it was 0.02. You have PSA anxiety. You are not alone.

This is the bane of the hypersensitive PSA test: Sometimes, there is such a thing as too much information. Daniel W Chan, Ph.D., is professor of pathology, oncology, urology and radiology, and Director of Clinical Chemistry at Hopkins. He is also an internationally recognized authority on biochemical tumor markers such as PSA, and on immunoassay tests such as the PSA test. This is some of what he has to say on the subject of PSA anxiety.

The only thing that really matters, he says, is: "At what PSA levels does the concentration indicate that the patient has had a recurrence of cancer?" For Chan, and the scientists and physicians at Hopkins, the number to take seriously is 0.2 nanograms/milliliter. "That's something we call biochemical recurrence. But even this doesn't mean that a man has symptoms yet. People need to understand that it might take months or even years before there is any clinical physical evidence.

On a technical level, in the laboratory, Chan trusts the sensitivity of assays down to 0. 1, or slightly less than that. "You cannot reliably detect such a small amount as 0.01," he explains. "From day to day, the results could vary -- it could be 0.03, or maybe even 0.05" -- and these "analytical" variations may not mean a thing. "It's important that we don't assume anything or take action on a very low level of PSA. In routine practice, because of these analytical variations from day to day, if it's less than 0. 1, we assume it's the same as non-detectable, or zero." 

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