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PSA reluctant to fall

Posted 05 Jul 2021 at 16:13

Hi all,

A question about how to interpret a stubborn PSA count.

A brief recap of the numbers, against a diagnosis of T2C N0M0 and a treatment plan of HT before RT:

June 2020 PSA 17. Started Bicalutamide and Prostap

Sept 2020 PSA 4.9

Dec 2021 PSA 10 Testosterone 7.9

Feb 2021 PSA 13.9 Testosterone 5.9 Swapped Prostap for Zoladex

April 2021 PSA 6.1 Testosterone 0.4

July 2021 PSA 4.2 Testosterone 0.6


I have my next onco appointment this week, so it's good to go in with  a view of what are the sensible questions to be asking. I guess the top question in my mind is- is the slowing fall in PSA a potential sign of resistance developing to the Zoladex , as it did last year with the Prostap?

It may be that the next step is the same in any case- give it more time to see if comes down, or not. But after a year on HT without, as yet,  getting to the point of throwing a 6 to start the RT game, it's a bit frustrating and I'd be interested in any views or insights. 


Thanks in advance,



Posted 05 Jul 2021 at 17:14

It is good that you have the Testosterone results as well as the PSA results, because without both sets of figures it would have been difficult interpret those results.

We often talk about cancer becoming HT resistant, but your case shows that we perhaps should be more precise in our words.

I am going to make two bold statements, I am not a doctor, so the following is my understanding of things:

1. Zoladex and Prostap, have NO effect on prostate cancer. They only effect Testosterone.

2. Testosterone (or lack of it) has an affect on prostate cancer.

Naturally because these hormones Zoladex/Prostap affect testosterone and that goes on to affect cancer, for shorthand we say that Zoladex/Prostap affects the cancer. In your case, it looks like a link in the chain got broken.

Prostap was not bringing your testosterone down (or at least not very much). So the cancer was still getting testosterone, The cancer had not become resistant to the treatment, the treatment was not working.

When you started Zoladex it did bring your testosterone down, and that has now affected the cancer and your PSA has came down.

I have no idea why Prostap did not bring your testosterone down. Andy62 will hopefully chip in here, as he has studied this in greater detail than I.

The next thing is that now you are on Zoladex and your testosterone is as low as it should go, is 4.2 for the PSA a good result? Well my PSA dropped from 22 to 0.8 after three months of Zoladex and then at the next test it was <0.1 . So yours has not fallen as far or as fast as mine did.

So yes the cancer may be starting to show an ability to thrive without testosterone which is a shame, but the RT may still be able to finish it off. I don't know what the plan is now, you have had six months of Zoladex, it has brought the PSA down slowly, do they wait until the PSA gets to 0.1 which would be ideal? or do they just say it probably ain't going to get lower let's just do the RT now?

I think I have got my understanding of how HT works correct, I would really like Andy62 or Lyn to chip in if I have made any glaring mistakes.


Posted 05 Jul 2021 at 18:39
There are two types of HT failure - a) the HT is not effective in bringing the man down to castrate level or below and b) the cancer becomes castrate resistant (e.g. it learns to survive without testosterone).

What your blood tests tell us is that the HT has brought you down to castrate level - so is doing what it is supposed to - but that your cancer is not being starved.

The onco might consider adding bicalutimide to the Zoladex to give it a bit more ooomph.

There is a third possibility and that is that you have a type of cancer that does not respond to HT; if you were my dad, I would be asking the onco to seek a review of the original biopsies to confirm that it is indeed adenocarcinoma and / or would be asking for a repeat of the biopsy to see if there are elements of large cell carcinoma or mucinous carcinoma. With a high PSA, small cell carcinoma is less likely unless you have a huge prostate?

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

Posted 06 Jul 2021 at 20:51

Dave, Lyn,

many thanks for the prompt responses- they were very helpful.

Yes, I learned the hard way to get testosterone scores at the same time as the PSA!

I will ask the onco about reassessing the  biopsy data , and let you know how it goes tomorrow. I won't be surprised to be put on a Bical booster, as this was mentioned as a possibility by his stand-in at our last meeting, when the PSA was at 6.1 ( coming down, but not rapidly, even then).

( My prostate was assessed as large , but not hugely so, so I am hoping we can put small cell  cancer to the bottom of the probabilities pile.......)



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