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GO BACK TO PSA 101

PSA - 28 DAY EXPERIMENT

Every man diagnosed with the disease is likely to continue having PSA tests for the rest of his life. There is an expression "PSA anxiety" in the prostate cancer world that sums up in a short phrase all the concern, worry, fear, apprehension, alarm, distress, unease, trepidation and dread that is associated with these ongoing tests. All too often a slight increase will escalate the decision to treat or re-treat on the assumption that the disease is spreading or recurring.

It has always been a concern of mine that men may make these decisions too soon. After all, there is ample evidence of the variability of PSA results (see PSA 101 if you have not read been there already) so care should be taken to make sure that there is evidence of a continuous rise before any action is taken.

There was considerable discussion on the now defunct PHML mailing list in 2001 about potential causes of variance in PSA levels. It was a suggested that there might be circadian (daily) as well as circa lunar (monthly) fluctuations. We could find no research on the subject so decided to run a small experiment, with two of us as guinea pigs. I volunteered to test the circa lunar theory by having 28 daily successive tests: another man volunteered to have tests every six hours for three days, although he didn't go ahead with this in the end. We had a quick fundraiser on the List to pay for my tests and away I went.

I had my blood drawn at noon each day and did what I could to stabilise the results by trying to follow exactly the same daily routine as far as sleep, food and exercise were concerned. I kept detailed records of all I did in case I could find any correlation between these activities and any variance in the results.

I have tabulated the results of the experiment below. The first week showed very little variance, but after that there were some considerable changes, the largest of which occurred between days 15 and 18, when there was an increase of 33%, from 4.50 ng/ml to 6.00 ng/ml. This was followed by an almost equivalent drop back to 4.60 ng/ml on day 22 - quite a week, and one which illustrates so clearly the importance of getting a series of tests done. I have highlighted these large changes in the chart.

 

RESULTS OF 28 DAY PSA EXPERIMENT
Sequence
PSA
% Inc/Dec
Sequence
PSA
% Inc/Dec
#1/28
4.90
#15/28
4.50
-6%
#2/28
5.00
+2%
#16/28
5.30
+18%
#3/28
4.90
-2%
#17/28
5.00
-6%
#4/48
5.00
+2%
#18/48
6.00
+20%
#5/28
4.90
-2%
#19/28
6.00
0
#6/28
5.00
+2%
#20/28
5.60
-7%
#7/28
5.00
0
#21/28
5.00
-11%
#8/28
4.90
-2%
#22/28
4.60
-8%
#9/28
4.70
-4%
#23/28
4.60
0
#10/48
5.20
+11%
#24/48
5.20
+13%
#11/28
5.00
-4%
#25/28
5.50
+6%
#12/28
4.70
-6%
#26/28
5.30
-4%
#13/28
5.00
+6%
#27/28
5.40
+2%
#14/28
4.80
-4%
#28/28
5.20
-4%
Median
5.00 ng/ml
Average
5.08 ng/ml

 

Figure 1 - Results of 28 day PSA experiment

The variance shown by these results is illustrated clearly in the chart below

Figure 2 - Chart of results of 28 day PSA experiment

There was some discussion about this experiment and one of the medical men on the List had this to say:

"Day-to-day as well as monthly fluctuations of some biological parameters are a fact are reported on salivary testosterone and cortisol, among others. It seems that a number of interacting factors would trigger similar fluctuations on blood PSA. Your experiment would tend to prove, rather than disprove, the value of PSA testing, as your results fluctuated within a relatively limited range. It would point out, however, to the advisability of repeat tests in borderline situations."

Note the comment that the range of the PSA numbers - from 4.50 ng/ml to 6.00 ng/ml - is regarded as relatively limited. This should be borne in mind for those marginal increases that cause so much bother to some men.

In 2007, one of the members of the PPML Mailing List analysed the figures in a different way and it may be of interest to see his take, which is on The Palpable Prostate blog at PSA Variation

Another issue that comes out of these figures is the question of PSA velocity, or doubling time. There are studies that relate speed of increase in PSA to aggressiveness and progression of disease, despite the fact that PSA is not prostate cancer specific. A doubling time measured in weeks or months is regarded as very dangerous, while a doubling time measure in years is regarded as somewhat better. It is also said that a velocity annual increase greater than 0.75 ng/ml is cause for concern.

An increase, as my tests in this experiment showed, from 4.50 ng/ml to 6.00 ng/ml in three days indicates an estimated doubling time of only 9 days and would also represent an increase double that regarded as 'safe' for an annual velocity increase, let alone one over three days.

Looking at all the figures in this experiment and using them to calculate a doubling time, produced an estimate of 229 days - a little under 8 months. Somewhat better than 9 days but still dangerously rapid and a clear call to action. Yet my PSA did not double in 9 days. It did not double in 229 days. In September 2003, two years plus since this experiment, my PSA went from the median of 5.00 ng/ml at that time to 6.25 ng/ml, well within the 'safe' figure of 0.75 ng/ml per annum.

In January 2005, after I had a TURP (Trans Urethral Resection of the Prostate) my PSA was 12.99 and it continued to rise after that. Details of what I decided to do are in my story.

 

 

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