Interesting. Plenty of discussion online about
the Gompertz model (a sigmoidal curve that is asymmetrical with the point of inflection), but essentially
all of it related to growth of
untreated ("unperturbed") tumors, which was overlayed to predict survival using a "death" size threshold (I'll talk about
the Myers comment in a second). The online literature primarily reviews how the model captures the tumor cells' dependence on the availability of nutrients, oxygen and space; as the tumor grows, the availability of these vital resources gradually decreases leading to a deceleration of the growth rate (and a theoretical limiting value). Not relevant to Redwing.
Thanks for the link to the Myers video...I think I've seen that one before; I remember him talking about
his wife watching the Redskins. It's a classic Myers rant--using a specific case study, as he loves to do--ranting on the notion (using the phrase I use often) that one-size(treatment)-does-
not-fit-all-PC-cases, or using his phrase, admonishing "rote treatment." This is a common Myers rant; a really important topic, but a recurring theme in his video series. In this instance, he rails
against the frequency which men (and their inept PC caregivers) prematurely jump-the-gun on post-RP SRT without "thinking" (as he gives a wry, almost mocking, smile), highlighting that for slow increases in PSA
there is no evidence that early SRT actually improves PC survivability...yes, SRT can knock-down the PSA, but he calls it a "numbers game" which only brings on worsened side effects without significant benefit. (He then goes on to warn of secondary cancers to the bladder or colon caused by PC radiation therapies, often some 10-years later, which too often in my view--and apparently his--gets inappropriately brushed aside as trivial especially for "younger" men who have life expectancy beyond 10 years.)
His brief mention of Gompertz modeling in the video seems very different than your case, Redwing. Here, he's talking about
a post-surgery case (not post-radiation) in which normal, benign, residual prostate tissue is left behind. His rant dives into the importance of using ultra-sensitive PSA monitoring test post-treatment in this T3 example case, not the standard screening PSA test (and he ridicules the ignorance of not differentiating between the two tests, a la mattman's naïve post/comment). What he describes in the video is the Gompertz behavior of the residual prostate tissue which has frequently been observed to rapidly produce PSA initially but then limit-out at around 0.2 ng/mL; in other words (and perhaps obviously), the PSA doesn't continue to increase because
it's NOT due to cancer...thus the title given to this video: "When Recurrent PCa isn't Cancer."
Interesting, none the less...
Have you seen any discussion of Gompertz application to cases like yours? Or anything at all related to prostate tumors, or PSA? (Your numbers look great, btw; even with the generally "expected" exponential (or power) growth forecast of recurrent actual cancer (ie. not benign tissue), your PSADT is 2-yrs. The variations you are seeing are not at all unheard of, given your treatment choices...particularly using, as you have, the standard
screening PSA test which Myers discusses.)
Post Edited (Blackjack) : 4/3/2019 7:30:15 AM (GMT-6)