Effect of Avodart on PSA

Hello everyone,

I'm hoping someone knows more about Avodart than me.

I was diagnosed almost 5 years ago with a 1 from 6 biopsy, 5% involvement and 3+3=6. PSA at diagnosis was 5.20 and prostate volume 93 cc.
A repeat biopsy 20 months later when PSA was 5.55, went 1 core from 20, also 3+3 and 5%. I have been doing active surveillance since then with 3 monthly PSA tests. The highest my PSA got was 6.83 in September, 2010.

With a large prostate, I have been having the expected urinary issues, so in January, 2011, I started on Avodart. PSA at that time was down slightly to 6.28. I was hoping for an improvement in urinary function and also the added benefit of a slowing in prostate cancer progression due to the blocking of testosterone conversion to dihydrotestosterone, which is alleged to be the main driver of cancer cell growth. I am also aware that Patrick Walsh believes that last statement not to be true.

All the information on Avodart advises to expect a PSA reduction of 40% after 4 months and 50% after 6 months and thereafter. I have not been able to find any clinical trial data where these percentages were established - it just gets stated everywhere. Anyhow, my personal experience is PSA down 22% after 4 months, and down 33% after 7.7 months, a much slower rate of reduction than the published data.

I had a look around the internet on forums and couldn't find much case history on the actual PSA reduction after commencing Avodart as a stand-alone therapy. But from the three cases I did find, only one man achieved a 50% reduction in PSA after 6 months. The second had a 29% reduction after 4.5 months and 46% after 9 months. The third bloke had an 18% reduction after 3 months, 24% after 6 months, 34% after 8.5 months and 51% after 11 months. This third case was a similar rate of PSA reduction to me. Has anyone reading this had a similar much slower rate of reduction in PSA ? I was trying to think of a reason for the slower rate of PSA reduction and wondered if Avodart caused more of a actual cc volume reduction with time rather than a percentage reduction in a particular time. That might explain why someone like me who started off with a really large prostate would experience a slower percentage rate of reduction on Avodart.

Also, what I am wondering is what is the reason that PSA goes down with Avodart. We know that Avodart causes a prostate volume to shrink and the conventional wisdom is that the PSA produced by a benign prostate is directly proportional to its volume. But they seem to say that Avodart only causes a 30% reduction in prostate volume, but a 50% reduction in PSA. So what causes the extra 20% reduction in PSA ? Does Avodart have the effect that not only does it reduce the size of a prostate, but also reduces the amount of PSA expressed per cc or gram of prostate tissue ?

And what effect does Avodart have on cancer cells other than the suggestion that it prevents the formation of dihydrotestosterone, the alleged villain ? Does Avodart also reduce the volume of prostate cancer cells in the same way that it reduces the volume of benign cells ? Does Avodart have any effect on the production of PSA from cancer cells, or is the PSA production from the cancer go on unchanged ? If PSA produced by the cancer is the same after taking Avodart, then it can be presumed that someone who has a significant proportion of their PSA coming from cancer cells, wont have a 50% reduction in PSA, but a lesser percentage due to their prostate volume reduction.

I would just like to get a better understanding of how Avodart works and any personal experience or other data would be really appreciated. Thanks.

Brian in Australia.

The cancerous prostate cells can give off much more PSA than benign normal cells relative to their volume. As I recollect, the benign cells give off .66 PSA per cc and G6 give off either 3 or 4 PSA per cc. Thus, dimmenisioning the DHT can help shrink cancerous cells and have a greater proportionate PSA reduction than the shrinking of the benign cells. This reduction is less as the Gleason score increases so the effect is not as pronounced in someone with a higher Gleason.

As to the actual percentages and time frame that is going to vary amoung individuals as you are learning. Your reductions are easily within the range that would support the overall averages you have sighted. I view you PSA decreases in line with expectations so far, based on my understanding. What do your docs say?

Finasteride and dutasteride work great for men who do not have PC....But once PC is diagnosed, (as in your case) their ability to suppress PSA levels let alone cancer, vanishes and PSA levels can increase with frightening speed as the cancer progresses unhindered by these drugs..This seems to be especially true with the higher Gleason grades..

I am unsure that az4peaks articulates a consensus view on doubling PSA score, after maintenance on Avodart, in order to get an accurate measure of PSA. Another view is that after six months on Avodart, one gets a new PSA baseline. Not all men see their PSA drop, and it is not clear that men who do not see a PSA drop have increased risk of malignancy.

Post Edited (jxmuldoon) : 9/19/2011 6:56:25 AM (GMT-6)