How many PC cells needed to detect PSA?

[Polaris1]

Does anyone have an estimate of how many millions of PC cells are needed to move PSA from undetectable to detectable?

This is a question that has intrigued me (my PSA is currently undetectable following RP and SRT) since listening to the interview of Dr. Kenneth Pienta (UroToday video, Prostate Cancer Foundation 2019). In this interview, which was conducted by Dr. Charles Ryan, Dr. Pienta said, “So when we had bone scans, CT scans, MRIs, we said, ‘Oh, you need a thumbnail of tumor.’ It's a billion cells. That's what we see clinically. That's metastasis. Now with Axumin scans and PSMA imaging, we can go down to two or three millimeter deposits of tumor. That's still 25 million cells. But now that's going to be the new standard soon for defining metastatic disease.”

[Tall_Allen]

PSA leaks out into the serum because of the leaky blood supply that tumors generate. Cancer cells create the "soil" in which they prosper. For a tumor to generate its own blood supply I would guess there has to be at least tens of millions of cells. There are many smaller tumors that have no blood supply and therefore generate no PSA. That is why systemic therapy is so important., and why merely treating PSA is doomed to failure:

prostatecancer.news/2020/07...

[Polaris1 in reply to Tall_Allen]

Thanks for your comments and the link.

For someone like me, is there any other useful biomarker of progression besides PSA? (I understand there is no imaging technology that is useful when the PSA is undetectable.)

[Tall_Allen in reply to Polaris1]

PSA and bone ALP are the two basic ones. As the cancer progresses, there are a host of others (e.g., LDH, CEA, blood work, Cellsearch count, cell-free DNA, etc.) you will want.

[Polaris1 in reply to Tall_Allen]

Thanks. I appreciate your prompt response.

[Polaris1]

Thanks for your helpful comments.

[dac500]

I don't think there is a mathematical formula that links PSA to how many million cancer cells you have. Some cancer cells release more PSA into the blood stream than others. Increasing PSA could be a rough marker of disease progression. Some of us, including myself, often worry too much about PSA.

My journey began in 2011 with Gleason 3 + 3 (as shown in a biopsy), which was treated by seed implant. Then I went through a local recurrence followed by metastasis in 2018. Now, I am on ADT (Lupron/Eligard).

So, far I have been through two breaks. During each break when my PSA starts rising, I get jittery. Even though PSA could be erratic, I am amazed how well I can guess what would be my next PSA reading. On January 14 my PSA was 0.34 and I am guessing my PSA would be about 0.60 on March 2 when I go for the next blood work. Why and how I make is guess. Because my PSADT has been consistently about 2 months when I was diagnosed with lymph node metastasis (PSMA/PET scan and biopsy) and during the two breaks I had since November 2018.

In about 4 weeks I would know how good my guess is. It would perhaps be the time to end the break. My testosterone is very slow to get above castrate level. During this break (last 3 month shot in March 2021), my testosterone remained <20 for six months and currently a little above 50.

[Polaris1 in reply to dac500]

It sounds like you are making use of your PSA readings and projections to make decisions. There don't seem to be any biomarkers other than PSA and ALP to guide these decisions.

[Hidden]

I was told that we can have 2-3 million pc cells not visible on any scans ., there is that .. the hidden element inside . I’ve had no signs or Psa over six years . Yet , #4 has no known cure . We kick the can .