Rise in PSA Beckman v Bayer

Hi Mr. Bill.

I have the same problem BTW figuring out to fully describe my case in 400 characters in the signature.

I also have similar questions about PSA doubling time. It would seem it's a heck of a lot easier to double a PSA of 0.05 to 0.10 since it only has to rise by a mere 0.05 than it is to double a PSA of 5 to 10, or from 10 to 20 etc.

I have read that the standard PSA is calibrated to be most accurate around PSA=4, and the ultra sensitive at 0.1. So yes my guess is in your case you should rely on the ultra sensitive one.

But then I revert back to my original question.

I am sure there are better tools to calculate PSA doubling times, but I just use http://www.timeanddate.com/date/duration.html which says there are 4 months and 25 days, or 146 days between your two dates.

You really need another sample in a month or three, but assuming your PSA velocity is straight line, you got 60% of the way (0.08) from 0.05 to double your 0,05 to 0.10 in 146 days. So doubling would occur at 244 days or about 8 months.

What that means in the case of such low values, we will have to defer to others, plus there is no guarantee that it is a straight line relationship, could be steeper or slower and another measurement is needed.

Rather than opt for 3 months, I would go with one or at most 2 month intervals to stay ahead of the curve as it were.

why did you need radiation after surgery, you said your psa was <.03?

david

T1cN0M1b-in-FL said...
Hi Mr. Bill.

I have the same problem BTW figuring out to fully describe my case in 400 characters in the signature.

I also have similar questions about PSA doubling time. It would seem it's a heck of a lot easier to double a PSA of 0.05 to 0.10 since it only has to rise by a mere 0.05 than it is to double a PSA of 5 to 10, or from 10 to 20 etc.

I have read that the standard PSA is calibrated to be most accurate around PSA=4, and the ultra sensitive at 0.1. So yes my guess is in your case you should rely on the ultra sensitive one.

But then I revert back to my original question.

I am sure there are better tools to calculate PSA doubling times, but I just use http://www.timeanddate.com/date/duration.html which says there are 4 months and 25 days, or 146 days between your two dates.

You really need another sample in a month or three, but assuming your PSA velocity is straight line, you got 60% of the way (0.08) from 0.05 to double your 0,05 to 0.10 in 146 days. So doubling would occur at 244 days or about 8 months.

What that means in the case of such low values, we will have to defer to others, plus there is no guarantee that it is a straight line relationship, could be steeper or slower and another measurement is needed.

Rather than opt for 3 months, I would go with one or at most 2 month intervals to stay ahead of the curve as it were.

Doubling time (PSA) is a surrogate for the speed at which a tumour is growing. The cells do not actually increase in size (normally) but rather increase in number. Much the same as an embryo grows ---- each cell divides in two at a specific rate. 1 cell becomes 2 then 4 then 8 etc etc. Likewise a tumour ----- each tumour cell divides into two identical cells at a certain pace. All this means is that doubling time is a measure of how long it takes the cell(s) to split into two and double in number and thus the tumour in size. If this process is slow (say 18 months) and the initial amount of tumour present was low, it will take a very long time before the tumour becomes life threatening. If the doubling time is very short then the division is fast and consequently will become life threatening much earlier. Theoretically it should take the same amount of time for PSA to double from 50 to 100 as it did from .5 to 1.

Post Edited (BillyMac) : 5/2/2013 12:22:52 AM (GMT-6)

Thanks BillyMac. I now better understand the theory, just seems counter intuitive.

Kind of the opposite of if you keep cutting something in half, you will always have some left, of the one from math class way back when if you are on the opposite end of a park bench from an attractive person of opposite sex, and continually cut the distance between you in half, the theoretical mathematician says you will never get there but the practical one knows when it's close enough for all practical purposes.