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Can anyone explain this? [Sudden PSA doubling-time slowdown]

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Posted 10/31/2016 5:35 PM (GMT 0)
Following RP, SRT, a nano-iron MRI in Nijmegen, then in Feb-May 2015 radiation to 8 lymph nodes para-aorta and common iliac combined with four months of Firmagon that sent my PSA to undetectable, this year my PSA doubling times were running about 2.5 months. However, starting in September there has been a sudden rise to over 18 mths. Could this possibly a delayed effect of the radiation? Any other explanation? Trying to prepare for an 11/3 meeting with my MO. Thanks.
Posted 10/31/2016 6:19 PM (GMT 0)
PSADT can be very unstable.
"PSADT in BRPC may naturally increase over time in the absence of therapy and may be influenced by duration of PSA follow-up."
The effect of the frequency and duration of prostate specific antigen (PSA) measurement on PSA doubling time calculations in men with biochemically recurrent prostate cancer
Posted 10/31/2016 6:42 PM (GMT 0)
Looks like you may be going back on the ADT......
Posted 10/31/2016 7:18 PM (GMT 0)
TA--yes, agreed, but going from 2 1/2 mths to 18 mths so abruptly?
Posted 10/31/2016 8:19 PM (GMT 0)
As it says, "46% of patients experienced PSADT increases >200%." It is not unusual.
Posted 10/31/2016 9:31 PM (GMT 0)
TA:

What a fascinating article. It's kind of a double -edged sword.
The good news is that someone like me, with a lousy PSADT (1.45 months!), might find that it slows down over time (ie: lengthens). That's good. The bad news is that we often use PSADT as an endpoint to show impact of some sort of tx. But if the PSADT lengthens, it may NOT be due to the drug. That's kind of disturbing.

At some point, maybe there would be enough information to factor in the natural PSADT, but somehow I doubt it.

Mel
Posted 10/31/2016 11:13 PM (GMT 0)
For some guys, PSADT is like clockwork; for others, not so much.
Posted 11/1/2016 6:28 AM (GMT 0)
I had a lot going on yesterday, but wanted to hear from The Tall One before his change of schedule. Therefore I was responding before I had a chance to read the study, for which I apologize. Having now read it (1 am), it did not really change my question (although it was fascinating and, as Compiler noted, has a big impact on the interpretation of trials, and the seven who went negative PSADT had infinite percentage moves though it does not say over what period of time or at what PSA levels).
My doubling time has suddenly, measured from recent low to recent high, jumped by over 900% or, from rough average PSADT before and after, by over 700%. While welcome on the one hand, it sure changes the plan which had been for a clinical trial of Prostvac or Apalutamide. I am now over the max for both. Thanks to all who responded, and I remain open to any hypothesis.
[And the title of this thread should probably refer to a sudden increase in PSA doubling time, not a slowdown.]

Post Edited (Cigafred) : 11/1/2016 4:58:27 AM (GMT-6)

Posted 11/1/2016 9:04 PM (GMT 0)
Tall Allen already responded, but in the same vein:

Drawing a graph with only two data points can be very misleading...
Posted 11/2/2016 2:11 PM (GMT 0)
On Inspire I was referred to a chart that looks like my experience so far. http://ppml-info.org/PSAlog.jpg
So I would say "case closed, happens after ADT."
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