Dr. Peter Black (biography and disclosures)
What I did before
Screening for prostate cancer has been conducted by many general practitioners and most urologists for years without level one evidence supporting its use. Most of the data on which we base our screening practices is indirect and not definitively causally linked to the decrease in mortality that has been observed in prostate cancer in the last 15 years. Critics pointed to the anxiety associated with an elevated PSA, the potential complications of prostate biopsy and the risks of over detection and over treatment of prostate cancer.
What changed my practice
It was hoped that some of the controversy around PSA screening would be put to rest with the completion of two large prospective randomized trials. Interim analyses were published from both trials in 2009. The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial randomized 76,693 men in 10 U.S. centres to PSA screening versus “usual practice”. The analysis after a median of 7 years revealed no difference in rates of survival from prostate cancer.1
The European Randomized Study of Screening for Prostate Cancer (ERSPC) randomized 182,000 men in 7 countries to screening versus no screening. This trial revealed a 20% decrease in mortality from prostate cancer after a median of 9 years in the screening arm.2
The PLCO study is criticized for the high contamination in the “usual practice” group – 52% of patients in this arm received PSA screening during the study. Also, the follow-up was relatively short. The European study is criticized because screened patients were more likely to have their prostate cancer treated at a tertiary care centre, although the authors have shown that cancers were treated similarly when adjustments are made to control for the stage distribution. The biggest point of contention in this study, however, is that 1410 patients needed to be screened and 48 needed to be treated to save one death from prostate cancer. These numbers are comparable with the numbers needed to screen for other cancers (for example: 800-1700 for mammography and 1200 for fecal occult blood to prevent one death from breast and colorectal cancer, respectively). The number needed to treat, however, is very high, and compares unfavourably with breast cancer, for example, which is generally estimated between 10 and 15.
What I do now
The controversy around PSA screening persists, as the studies are interpreted by different parties as either supporting or detracting from the argument for prostate cancer screening. The mandate remains in large part the same – we must provide our patients with the necessary facts for them to make an informed decision whether they would like to be screened or not – but we now have much higher quality information to offer our patients in this decision process.
From the urologist’s perspective, it would appear that two key factors on the horizon are going to swing the pendulum strongly in favour of PSA screening: 1.) As the screening studies mature, the numbers needed to screen and to treat are going to come down markedly, as is evident in a recent publication from Sweden3, so that the cost, both in financial terms and with regard to potential patient morbidity from screening, will be drastically reduced; and 2.) We must learn to disconnect the diagnosis of prostate cancer from its automatic treatment. Many patients that we have treated with surgery or radiation therapy in the past are suitable for active surveillance. If we are able to limit treatment to only those cancers that need treatment in order to enhance the quality and longevity of the individual patient’s life, PSA screening will become a more valuable tool.
References: (Note: Article requests require a login ID with the BC College of Physicians website or with UBC)
- Andriole GL, Bostwick DG, Brawley OW, et al: Effect of dutasteride on the risk of prostate cancer. N Engl J Med 362:1192-202, 2010 (View Article with CPSBC or with UBC )
- Schroder FH, Hugosson J, Roobol MJ, et al: Screening and prostate-cancer mortality in a randomized European study. N Engl J Med 360:1320-8, 2009 (View Article with CPSBC or with UBC)
- Hugosson J, Carlsson S, Aus G, et al: Mortality results from the Goteborg randomised population-based prostate-cancer screening trial. Lancet Oncol, 2010 (View Article with CPSBC or with UBC)