Beware over-reaction to ultrasensitive PSA doubling times

It is not exactly “new” news that PSA doubling times calculated using low levels of ultrasensitive PSA data can be very different to those calulated using standard PSA values. However, a new paper has provided some additional data on this issue.

Reese et al. have used data from the CaPSURE registry to compare PSA doubling times in 394 patients, all of whom were treated first with radical prostatectomy, who subsequently had a rising PSA level, and who had their PSA doubling times calculated using ultrasensitive and standard PSA values prior to making decisions about next therapeutic steps.

Tehir stiudy showed that:

  • The average (median) ultrasensitive PSA doubling time was 11.9 months (a year).
  • The average (median) standard PSA doubling time was 240 months (20 years).
  • Agreement between ultrasensitive and standard PSA doubling times was poor.
  • Ultrasensitive PSA doubling times were more or less rapid than standard PSA doubling times by more than 15 months in 244/394 men (62 percent) and 35/394 men (9 percent), respectively.

The authors conclude that “Ultrasensitive prostate specific antigen doubling time is often significantly more rapid than traditional prostate specific antigen doubling time, potentially overestimating the risk of clinical recurrence.”

It is worth remembering that availbale PSA doubling time calculators are almost all based on data generated using standard PSA test data, and so PSA values of 0.2 ng/ml or less may not be accurate when used in such calculators. In the words of Reese et al., “… the decision to proceed with salvage therapy should not be based on prostate specific antigen doubling time[s] calculated using ultrasensitive prostate specific antigen values” — at least until we have validated calulcators based on ultrasensitive PSA data.

Most good specialists in the management of prostate cancer are already well aware of this, however, and are very careful not to over-interpret small rises in PSA level indicated by an ultrasensitive PSA test. It is often wise to look at such data from ultrasensitive PSA testing more appropriately as a potential signal for close monitoring rather than a signal for immediate action.

3 Responses

  1. One year ago my PSA was 0.1 mcg/l, it had been thus from the time my ADT and EBRT commenced about 4 years ago. I always had the PSA test done every 3 months, so the tripling from one test to the next was quite a shock. I have T3b, Stage 3, Gleason 8, not on any meds at all, yet my oncologist only wishes to see me annually, last visit in October 2011.

    So my last four tests have given results of 0.3 mcg/l. What is your advice on this? Is the cancer on the march all the time and is there something else I should be doing? A reply from a knowledgeable person by e-mail to me would be greatly appreciated.

    Mike Feorais

  2. Dear Mike:

    I see you live in Ireland, so my first question is, “Who has been giving you the PSA tests every 3 months? Is it your local general practice doctor?”

    So long as your PSA is stable at 0.3 mcg/l (which is the same as 0.3 ng/ml), as it has been for the past year apparently, I would see no particular reason for you to be seeing your consultant oncologist more than once a year. A stable PSA of 0.3 ng/ml is low and suggests no sign of disease progression. On the other hand, if your PSA was to jump again … up to say 0.5 ng/ml or higher … then I do think it would be wise for you to ask your GP to arrange a follow-up visit to see the consultant.

    What is really important here is not so much your absolute PSA number if it is low like this, but the speed at which your PSA is rising (the PSA doubling time). At the moment, that is zero … which is great!

  3. Hello Sitemaster! Amen to your explanation regarding PSA elevation. As regards this gentleman from Ireland, he is still within a time-frame that he could also experience a “bounce/bump” in his PSA that should still be monitored rather than jumping to the conclusion that he has recurring prostate cancer. In the meantime, as you make note, his PSA level looks great and apparently stable.

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