Monitoring post treatment PSA + ???

[mperloe]

While monitoring PSA or PSA doubling time is easy enough, some patients will have tumor progression despite normal PSA and DTPSA.

It would seem that both MRI and CT scan might pick up enlarged lymph nodes and perhaps bone mets, the X-ray exposure with CT offers little return benefit. The question is whether PSMA PET (not Axumin which is less sensitive) will be used only after PSA rises, for diagnostic staging in new patients or for post treatment monitoring.

I've seen some MDs use CEA, CA19-9, CA15-3 and CA125 as part of the monitoring regime. Whether liquid biopsies will be helpful is also unclear. While tumor markers such as urinary micro RNA for initial prediction of a cancer diagnosis, microsatellite instability and tumor burden have been useful in endometrial, GI and melanoma to predict immunotherapy benefit they don't seem to be helpful for prostate cancer.

[GP24]

You can get a PSMA PET/CT every year and see if any new lesions can be detected. At a PSA value of 0.4, which you currently have, you do not need to spend the money on that.

[mperloe in reply to GP24]

But My initial PET that was done 3 months post Tulsa Pro was .3 and showed the seminal vesicle lesion.

[GP24 in reply to mperloe]

What do you mean with "was 3"? I had fiducials placed in my affected seminal vesicle and got it radiated with Cyberknife then.

[mperloe in reply to GP24]

TYPO. The PSA was only .3 at the time the PET was positive. So abnormalities may still show up with low PSA in up to a third with PSA less than .5

[GP24 in reply to mperloe]

It depends what you want to decide. If you want to decide to do salvage radiation to the prostate bed only or plus the pelvis area, a PSMA PET/CT at very low PSA levels showing one affected lymph node will make you treat the pelvis too. Even though there are probably more mets. If the lymph node is outside the radiation area you may skip the entire salvage radiation.

I prefer to do a PSMA PET/CT above 2.0 ng/ml so that I see most of the mets which have a sufficient size for the PET/CT.

[mperloe in reply to GP24]

Thanks. My story is a bit convoluted and not really similar to any of the trial subject groups. I had a PSA of 3.77 at discovery, followed by 3TmpMRI, with a GL4+3 lesion with cribriform pattern. Because of Covid, I opted to do a PET scan three months later when PSA was down to .3. When the lesion was seen, we opted for ViewRay.com MRIdian SBRT with 5 treatments total 42Gy to the prostate. Post SBRT I now have a PSA of 0.014. I’m three months into a 6 month course of ADT +abiraterone+prednisone. As I entered all this on T prior to diagnosis, I expect to run a T around 100ng/dl off ADT+abi after stopping. We will monitor and if after 3-6 months, we might consider low dose T to get the level between 250-300ng/dl. The question is since we’d likely see a rise simply from the testosterone rise, or possible a post radiation bump, how would it be determined that the elevated PSA was not a biochemical recurrence. It seems likely that PSA doubling time remains low or the PSA bounces around it is likely not indicative of tumor. I’ve recently heard med oncologists suggest that in the US PSA of 0.5 may allow for reasonable sensitivity, around 50% with the PET scan. Thanks for your comments.

[GP24 in reply to mperloe]

Since you already had salvage radiation to the prostate, your next steps could only be SBRT radiation to the detected mets, provided you do not choose hormone therapy only instead.

It does not matter if this is done at a PSA level of 0.5 or 4 ng/ml, SBRT will zap them. You should not have the objective to keep the PSA value below 0.5 ng/ml with metastases directed therapy. You have to fight the cancer, not the PSA value.

[mperloe in reply to GP24]

Agree if lesions noted on PET, then SBRT. If PSA doubling time is less than 10 months, and no lesion on PET would reconsider repeat triptorelin with either abiraterone again or darolutamide. We have an increasing number of options.