Editor—Gottlieb's news item reports that the reliability of prostate specific antigen (PSA) testing is poor.1 Necropsy studies have for a long time shown that the prostate of men over 50 harbours cancer in about 30% of cases, but only 8-10% develop a clinical cancer during their lifetime. That histological evidence of cancer is found when six or more biopsy samples are taken from the prostate is therefore not surprising. Screening studies also show that this happens below the classic threshold of a prostate specific antigen concentration of 4 ng/ml.2
Most of these cancers are overdiagnosed and would never be symptomatic during lifetime or cause death. This has been estimated repeatedly from screening data.3,4
The aim of screening with prostate specific antigen is to reduce mortality and save lives, not to detect histological, non-aggressive cancer, which is to be avoided. Using a cut-off point of 4 ng/ml already allows for great diagnostic anticipation and considerable overdiagnosis.
Lowering this threshold needs to be carefully considered. It will result in more biopsy specimens showing cancer but also greater overdiagnosis. Whether it will increase screening efficacy (mortality reduction) is unclear and remains to be shown. Waiting for the results of ongoing screening randomised studies would be a more reliable option.
Competing interests: None declared.
References
- 1.Gottlieb S. Study shows poor reliability of prostate cancer test. BMJ 2003;327: 249. (2 August.) [Google Scholar]
- 2.Schroder FH, van der Cruijsen-Koeter I, de Koning HJ, Vis AN, Hoedemaeker RF, Kranse R. Prostate cancer detection at low prostate specific antigen. J Urol 2000;163: 806-12. [PubMed] [Google Scholar]
- 3.Ciatto S, Zappa M, Bonardi R, Gervasi G. Prostate cancer screening: the problem of overdiagnosis and lessons to be learned from breast cancer screening. Eur J Cancer 2000:36: 1347-50. [DOI] [PubMed] [Google Scholar]
- 4.Draisma G, Boer R, Otto SJ, van der Cruijsen IW, Damhuis RA, Schroder FH, et al. Lead times and overdetection due to prostate-specific antigen screening: estimates from the European randomized study of screening for prostate cancer. J Natl Cancer Inst 2003;95: 868-78. [DOI] [PubMed] [Google Scholar]