The USPT has concluded that men should not be screened for prostate cancer with a PSA assay. In a blog that I follow, DB concurred with this recommendation. In his post, he gave a bunch of opinions and then said, “when one examines the data…” he agreed with the USPT recommendation.
I contend that to examine the data, means to read every word of the ERSPC and PLCO studies, question every assumption, every data analysis method, every result, every conclusion. This is examining the data although it does not mean that one will disagree. I have not examined the data although I remember hearing that a significant percentage of the control group was contaminated because they were screened for PSA.
Here are some possibilities for men who die of prostate cancer with the assumption that incurable prostate cancer is associated with cells that have escaped the prostate.
- Cells have escaped the prostate before any currently available detection method detects cancer, rendering current treatments (surgery, radiation) ineffective because the escaped cells are not treated.
- The current treatments are occasionally ineffective (cells are contained within the prostate but not all cancer cells are killed).
- The cancer is not detected until cells escape from the prostate, because no detection methods are used, especially no PSA test is performed.
- The cancer is not detected until cells escape from the prostate, because the detection methods generate false negatives.
Note: prostate is often compared to a walnut which is the picture.