PSA doubling time or PSADT is a valuable prognostic factor in assessing the need for second- or even third-line treatment in men with biochemical progression of prostate cancer.
However, one of the major problems in the use of PSADT is the fact that there is no “standard” method for calculating this factor — and different methods for computing PSADT can lead to inconsistent results, above and beyond the inevitable variability of the basic PSA data.
Ponholzer et al. set out to develop a standardized, reproducible method for PSADT determination which could also offer a mechanism to estimate PSADT error. Better still, they have made this PSADT calculator available on line, complete with graphic output.
If you want to use this calculator to assess your PSADT with accuracy,
- You need to know your last three PSA test results and the exact dates the blood samples were taken; the tests should all have been conducted at the same laboratory and using the same assay.
- There should be a period of at least 3 months between the first and the last PSA test.
- You should have had no medical treatment between the first and the third PSA tests.
- You should be sure you have had no infection, no prostate manipulation, and no problems with urinary retention during the time period.
- You should not subtract the nadir level from your PSA; use the actual PSA levels.
American readers should be careful to note that dates should be entered into the calculator using the European format of day, month, year (e.g., 23.05.2010) and not the American format of month, day, year (e.g., 05.23.2010).
The authors are careful to point out that their tool is not any “better” than other tools that are available, but it is based on a standardized “least squares” error methodology, and it is available for anyone to use for free!