Authors Sandblom G, Varenhorst E, Rosell J, Lofman O, Carlsson P.
Review Date Apr 2011
Citation BMJ Mar 31;342:d1539. doi: 10.1136/bmj.d1539 (online before print)
The debate about the effectiveness of prostate cancer screening with PSA testing continues, with conflicting data on whether screening significantly reduces prostate cancer mortality and debate on whether the risks of over-diagnosis and overtreatment are outweighed by any mortality benefits. One of the difficulties is that many studies have had relatively short follow-up periods. This is the first study to publish 20-year data.
To assess whether screening for prostate cancer reduces prostate cancer specific mortality.
Design: Population-based randomised controlled trial.
Setting: Department of Urology, Norrköping, and the South-East Region Prostate Cancer Register
Participants: All men aged 50-69 in the city of Norrköping, Sweden, identified in 1987 in the National Population Register (n=9026).
Intervention: From the study population, 1494 men were randomly allocated to be screened by including every sixth man from a list of dates of birth. These men were invited to be screened every third year from 1987 to 1996. On the first two occasions screening was done by digital rectal examination only. From 1993, this was combined with prostate specific antigen testing, with 4 µg/L as cut off. On the fourth occasion (1996), only men aged 69 or under at the time of the investigation were invited.
Main Outcome Measures: Data on tumour stage, grade, and treatment from the South East Region Prostate Cancer Register. Prostate cancer specific mortality up to 31 December 2008.
In the four screenings from 1987 to 1996 attendance was 1161/1492 (78%), 957/1363 (70%), 895/1210 (74%), and 446/606 (74%), respectively. There were 85 cases (5.7%) of prostate cancer diagnosed in the screened group and 292 (3.9%) in the control group.
The risk ratio for death from prostate cancer in the screening group was 1.16 (95% confidence interval 0.78 to 1.73). In a Cox proportional hazard analysis comparing prostate cancer specific survival in the control group with that in the screened group, the hazard ratio for death from prostate cancer was 1.23 (0.94 to 1.62; P=0.13). After adjustment for age at start of the study, the hazard ratio was 1.58 (1.06 to 2.36; P=0.024).
After 20 years of follow-up the rate of death from prostate cancer did not differ significantly between men in the screening group and those in the control group.
Points to Note
- Advantages of the study are: the follow-up period is longer than in other published trials (cf 2009 publications for European and American trials); there was little background screening in Swedish men during the study period; and Sweden has good quality population-based data and registers to conduct such a study.
- The disadvantage of the study is the small sample size, thus low power to detect small differences in mortality between screened and control men. Prostate cancer deaths occurred in only 30 of 85 cases in the screened group and 130 of 292 cases in the control group.
- Although the mortality reduction in the screened group was not statistically significant, the confidence intervals suggest that the reduction could be up to 1/3.
- The authors suggest that even if there is a reduction in prostate cancer mortality (that this study was too small to detect as statistically significant), the risks associated with over-detection and over-treatment are too high to support population screening for prostate cancer.
- Even after a study with 20-yr follow-up, the debate goes on.