How Low is "Undetectable" PSA after Prostatectomy?

Undetectable just means the reading was lower than their lowest threshold. About 5-6 years ago, ultrasensitive PSA was rather discredited in a large European study - too many men were being referred for unnecessary salvage treatment and tiny rises cause significant distress, often unwarranted. At that point, many hospitals/ urologists stopped doing any PSA reporting at lower than 0.1

For John's first few years, his readings were to 3 decimal points but this has been stopped - since the EU research was published, all his results are to 0.1; even if he has his PSA test at the private hospital, he still gets a <0.1 result because the private hospital uses the NHS lab for processing. The NHS lab has not got rid of all its ultrasensitive machines; it just has a policy of not reporting the u.s. result.

In your case, I suppose the question has to be directed to your urologist - if you had a small rise from 0.025 to 0.03 would they do anything or would you still need to wait for three successive rises above 0.1? If you would not be referred to oncology until you have 3 rises over 0.1, usPSA is only going to cause you angst with no obvious benefit 🤷‍♀️

There are many manufacturers making analysis machines, which all (as far as I know) are capable of testing for different things, not just PSA. For any given test, an assay provided by the manufacturer is required, and these are available with different lower limits depending on the precision you require, but it also takes longer to do higher precision tests (and also very high PSA test values have to be diluted and retested to bring them within the max range). Some of the support groups had testing machines some years ago which were used for testing events, and GFCT could also lend them. (This is no longer the case.) IIRC, each assay could do something like 7 or 9 tests (I forget), with about 15 mins to get 0.1 resolution with the assay we were using for PSA screening tests at the time. (I might guess that larger non-portable machines in hospital labs might be able to work faster.) We did one event where we managed to have 3 machines running in parallel, and that could keep up with a couple of phlebotomists drawing blood to give results in real-time, 15 minutes after the blood draw.

The common lower limits I see at various different hospitals are: 0.1, 0.03, 0.025, 0.01, 0.003 - some of this may be the assay used, but I suspect figures like 0.025 may be the maximum time they're prepared to allow the test to run with the assay being capable of higher resolution, because a lower limit with more than one significant digit doesn't make much sense oherwise.

The hospital where I had radiotherapy (but not usually any blood tests) only measured down to 0.1. In a review of their cancer services which was done by the Christie (after my treatment), they were told this wasn't good enough, and they now send PSA tests to another hospital and get results to 0.01. My own district general hospital (which only does diagnosis and post-treatment monitoring, but not any treatments other than chemo and immunotherapy), has measured down to 0.01 all through my treatment, and my consultant at my treatment hospital advised me to get blood tests done at my DGH for this reason.

The higher resolutions are more important for prostatectomy patients, but that includes salvage radiotherapy patients. Some main centres now use the rise well before 0.1 (combined with other data such as histology) to act before 0.1 of followup treatments.

I'd also seen comments here about accuracy of readings below 0.1. Certainly with mine, there appears to be no noise in those readings given to an accuracy of 0.01, such that although they're reported to a resolution of 0.01, I suspect they may be measured more accurately than that, because they are all completely consistent.

Last year's Tackle conference had a talk on a new portable PSA testing machine. They way they seem to be certified is by cross-checking the results of samples in lots of different ranges against about 20 other test machine models and assays. There is a bit of variation between machines/assays, so it's good to always have your tests done by the same lab to remove this noise, but any one model of machine and assay seems to be very consistent.

Edited by member 14 Apr 2023 at 08:52  | Reason: Not specified

Hi Jedsee,

My husband is tested at a lab that tests to 0.025 aswell. He was less than that (so undetectable) for over 12 months post op. It then rose to 0.029 and six weeks later 0.044, I’m having his test done at the 6 week point again but wish I knew the actual numbers of the first 12 months as I could monitor better how quickly it has been rising. We have appointments with urologists in may so should start to have a plan then. 

Within a year of my prostatectomy, my PSA went from 0.014 to 0.015 to 0.019 to 0.023.

With 3 successive rises, my Oncologist recommended radiotherapy.  

But I was pT3b and had positive margins and was Gleason 9.  It was always suspected that I'd need salvage radiotherapy at some stage.

Your Oncologist looks at the psa and all the other bits of your personal data to inform their decision making.

That said, I'm glad of the ultra sensitive results I got.  Were I with a different hospital which only measured to one decimal place, how long would I have waited for my salvage treatment and risked the cancer spreading?

My PSA has been <0.006 since salvage radiotherapy and hormone therapy. 

Ask your doctor for a copy of the blood report. Depending on lab kit available you’ll get varying resolutions and sensitivity. Be aware at low levels  ~0.006 these can move around a bit due to calibration/noise/error so don’t be alarmed so long as three sets of bloods don’t come back and show an continued increase. Even then anything <0.1 is a good result. For me I won’t started twitching <0.03 and for three year thankfully I’ve been usually <0.006.

I told my GP front of house staff I would like a copy of the blood report for my records as I’m dealing with different parties so easier to ensure there is one central repository for all the data. Works well 🙂 

Bit of a learning and mindset curve this stuff 😵‍💫🤪

Edited by member 15 Apr 2023 at 19:29  | Reason: Not specified