Low PSA, MRI shows likely cancer

PSA is just an indicator and an imperfect one. You have have exceptionally high PSA and not have cancer or very Low PSA and have it. As I've heard it mentioned by others, it's a "check engine light" is all. I"m sure PSE and/or biopsy would be next steps. If it's slow growing then your doc is correct, he'll die WITH prostate cancer rather than FROM it - but you won't know that until more tests, and one of the best ones is a decipher test, which can determine the likelihood of the cancer being more aggressive and worth more attention (this after a biopsy).

ziggydeep, some prostate cancers tumors don't produce PSA; some prostate nodules are not cancer.

The next test is usually a PET/CT That will tell you if the nodule is using a lot of sugar, which would increase the suspicion of cancer. I assume your spouse will have a biopsy no matter the PET/CT results.

The biopsy will confirm or rule/out cancer. If it is cancer, the biopsy will yield a gleason score, giving you an idea of the tumor type and a choice of watch and wait or treatment. https://www.pcf.org/about-prostate-cancer/diagnosis-staging-prostate-cancer/gleason-score-isup-grade/
The biopsy sample can be sent for somatic testing--testing of the mutations specific to this tumor.
When he has a biopsy, make the request for Decipher Testing to be sure they retrive a large enough sample.

Meanwhile, ask for a PSE serum test. It's fairly new and said to be 94% accurate. But it isn't commonly ordered.
https://www.94percent.com/
https://www.veracyte.com/decipher-prostate/
Treatment for prostate cancer has gotten so good that they tell all of us that you have to die of something else.
Best wishes

Some people with prostate cancer do not produce much PSA at all. This has been found in about 10% of cases. One test you can do if the PSMA pet test doesn’t show up anything is that can do a FDG pet test which can find cancer that doesn’t produce PSMA.

Not producing PSA does not mean you don’t produce PSMA but they are somewhat related.

After the MRI they should’ve given you a PIRADS Score for the metastasis they found in the prostate. A score of one or two pretty much means you don’t have anything.

If you really want to find out whether or not there is cancer, before doing a biopsy, you can do a PSE test. That will give you about a 93% chance of knowing whether or not there is cancer Even though the PSA is very low.

I had a PSA below 1. My internist did a DRE (digital exam) and found a nodule. It turned out to be an aggressive prostate cancer. I had a prostatectomy. The cancer returned 14 years later and I had 37 external beam radiation treatments. Since then, my PSA has been undetectable.

A small, but significant, percentage of men have prostate cancer which does not produce PSA. I repeatedly thank the internist who did the DRE--something many doctors do not perform and claim is unnecessary. I urge all men to get a DRE as well as a PSA. The Urologist I saw after the nodule was discovered had to be talked into doing a biopsy because he said I couldn't possibly have prostate cancer with such a low PSA.