Why do different cancer centers use different PSA undetectable limits?

@jeffmarc wrote ❝One reason is, it takes a couple of more days to get the results❞

That would be related to Kaiser's logistics, not the test itself. Sometimes my uPSA results pop online on MyChart in as little as an hour after they draw my blood, though 2–2½ hours would be more typical.

It was genuinely useful for me recently to have the more sensitive test.

The MRI showed a new area of new lucency around where I had my spinal surgery on the lesion in 2021. It's most likely benign bone remodeling, but we can't biopsy it because of the cement and metal rods blocking the way in.

If my PSA test went down only to 0.1, there would be a very small risk that I actually had a new tumour growing. It's very rare for prostate cancer to progress with PSA that low, but as you've mentioned here in the forum, there are documented in cases of it.

However, there are no documented cases that I or my oncologists are aware of where cancer progressed with PSA below 0.01, so we're confident just monitoring that spot regularly for changes rather than giving it a precautionary dose of radiation, especially with ALP (the main bone-distress indicator) well down in normal range, and LDH (a non-specific indicator of bone or muscle strain) stable since 2021.

@sandguy

As far as I know, for most cancers "7 years" of no evidence of disease usually means "probably cured". PC is not unique in that way, other cancers can return also. Doctors for that reason prefer the term "remission" and I personally think that it is a correct term. You can just say that tests show no evidence of disease and that only future will tell if you were completely cured or not, which is actually the truth.
Wishing you forever "less than 0.03" ; ) !!!

@jeffmarc
Thank you, as always, Jeff, PC guru! Plus thanks to many others who have weighed in.
In terms of Gleason score, it's interesting in my case. The initial biopsy had found some 3+5, but I think after surgery that was downgraded.
Please indulge me as I paste in some of the significant "FINAL PATHOLOGIC DIAGNOSIS:"
Adenocarcinoma, Gleason pattern 3 + 4 = 7 with tertiary pattern 5, grade
group 2+, organ confined
AJCC 8th edition stage: pT2 N0
Prostate Weight in Grams (g): 30 g
Minor Tertiary Pattern 5 (less than 5%): Present
Percentage of Pattern 4: 21-30%
Cribriform Glands: Present, focal
Estimated Percentage of Prostate Involved by Tumor: 6 - 10%
Greatest Dimension of Dominant Nodule in Millimeters (mm): 13 mm
ADDITIONAL FINDINGS
High-grade prostatic intraepithelial neoplasia (PIN)
Nodular prostatic hyperplasia

So, I don't know, I THINK that all sounds pretty good, doesn't it? I'm thinking this was taken care of fairly soon in the cancer's life cycle, even though I hadn't had my PSA checked for about five years. Or is the Cribriform an issue, possibly?

Thanks, all!

@sandguy
I like your results. I think the surgery removed all of the problematic tissue.. The PIN would’ve been removed as well as the cribriform which was just in isolated spots.

PT2 is good, not too aggressive, Gleason score nicely downgraded.

Overall a real positive result.

@surftohealth88 Yes, 7 years sounds like a reasonable variant of 10 years for a "statistical cure."

My doctor told me that, for radiation patients, they don't do the ultra sensitive test because we still produce PSA so super low numbers get into the "noise" category and can cause unnecessary worry. For example, I had SBRT and my PSA has now been "undetectable" 15 months since stopping Orgovyx but the report consistently says "< 0.04." I can live with that. However, if it was 0.03 and then went to 0.035 I would probably experience a lot of anxiety, then a lot of relief if the next time it was 0.025, etc.

@scottbeammeup 0.04 is pretty close to the ultrasensitive threshold (it's well below 0.1), but I agree with your main point. If the treatment goal isn't to reduce PSA to zero, then there's no point knowing that it went up from 0.01 to 0.04 last quarter, then dropped back to 0.02 this quarter. Like you wrote, it's just noise.

But in my situation (radiation to spine and prostate, 4¼ years on Orgovyx and Erleada), it's extremely comforting to know that my PSA has never once reached 0.01 or higher once it became undetectable.

@northoftheborder Definitely. It's two different measurements for those who had surgery and those who had radiation/ADT. Here's hoping you never reach 0.01!

@scottbeammeup wrote ❝Here's hoping you never reach 0.01!❞

Amen! If I can make it 9 more months with undetectable PSA, I'm officially in long-term remission (at least according to some ways of measuring). I know it's an arbitrary milestone, but it still means a lot to me.

Having been a the Director of Clinical and Anatomical Pathology Services ("The Lab") for much of my career, I can offer that lot of "normal ranges"/"reference ranges"/"cut-offs" are determined by the testing method and instrument on which the test is performed. Different vendors and their instruments might have very subtle variation from one another...but it is generally not "clinically significant", and their ranges are exceedingly close to each other. Lab medicine and the practice of medicine would be chaotic without normal ranges being the same or very close. There is one company known throughout the world who nearly prides themselves with the self-declared moniker of having the best testing methods in the world, and many of their test methods differ significantly enough from other vendors, that the have their own test name and normal range (example: they have a NT-ProBNP test with its own normal range, while the rest of the world uses the standardized BNP test). The rest of the world uses that company as a target for their often esoteric/unusual methodologies. It is a silly market-driven competitive battle for sales and market share, while each company truly believes that their method is the best. The bottom line is that their test methods result in different "normal ranges." Sometimes, even without considering that one outlier diagnostics company, there are still different methods on different instruments that test for the same thing. And...if the Lab is doing "good science", they are aware that different regions of the country actually see population dynamics and other factors determine what that "normal range" is. It may vary a bit from region to region...not by very much, and not by what we would call "clinically significant", but it will be different. When I say "clinically significant", the medical and clinical lab industry determined decades ago that a test result that varies by 10% or less is not "clinically significant"...such variation can almost be "expected." There is or can be enough random variation in testing methods during different times of the day or days of the week, that those subtle < 10% variances are expected. One of the "quality control" methods performed in laboratories is with the use of either a "Low", "Normal", and "High" (or all three) sample(s) being run once per shift (several times per day) to see if that real patient sample has changed over the course of the day. If it exceeds 10% variation, then that triggers further investigation as to "why?" It is especially true if two or all three of the samples (Low, Normal, and High) "all" changed. This is used most often in Hematology using, say the White Blood Cell Count (WBC), the Hemoglobin (the weight of the Hemoglobin protein in each cell), and Hematocrit (percentage of red blood cells to total liquid volume of blood). The Lab saves a tube from patients with a very low WBC, a normal WBC, and a high WBC (the Hemoglobin and Hematocrit usually comparatively parallel the WBC values, but not always). At the beginning of each shift in the Lab, those samples are run again to see if the instrumentation will produce the same result as it did during the previous eight hours. If the results are the same or within that 10% expected variation, then all is well. But if the results are outside that < 10% variation, further investigation is warranted. BTW...WBC's and other parameters in a tube used for a Complete Blood Cell Count (CBC) are labile...the cells breakdown within 24 hours or more (or at least become less reliable for that reproducibility), so those tubes are discarded or stored each day, and fresh, new samples are used for each new day. Anyway, "unexpected variation" indicates an instrument issue that needs investigation. In the Chemistry and Coagulation departments, another method is to use "pooled" patient plasma. The plasma from numerous patients is combined into large pools of plasma that is stored refrigerated or frozen. Such plasma can be purchased from commercial suppliers, but most labs create their own pools. Numerous testing runs determine the value of the pooled plasma for several individual tests in Chemistry, or one or two in Coagulation, to include acceptable variation limits, which are usually quite tight. Then once per shift or once per day, that pooled plasma is run like any another patient sample to see if the expected value is obtained. If it is, then it is determined that the instrument and testing method is/has-been stable. But...if the expected value is NOT obtained, then that triggers an investigation as to "why?" So...
I hope that explains why some tests in some labs and institutions have subtly different "normal ranges"/ "reference ranges"/"cut-off" values. What is important is the physician's ability to track "you" and "your" test values, such as your post-RP PSA values every three months for the first year. You hopefully go to the same lab to get your blood drawn, so that Lab is the one performing your PSA testing, using the same instrument and method each time ("apples to apples"). If you went to two or more different Labs during that time, each with its own testing method, and...when combined with the very tight < 0.1 ng/ml good value, but a 0.2 ng/ml value possibly indicating Biochemical Recurrence, that tight 0.1 ng/ml difference could be affected by a different Lab and testing method. So, make sure you use the same Lab every time. In fact, the test report usually has disclaimers about different Labs and testing methods, to include some statement like "no one, single determination can be used as an indicator of malignancy or no malignancy." Hope this helps!