Investigators have found that overdiagnosis of prostate cancer through prostate-specific antigen (PSA) screening is low in younger men—but rises sharply with age. The study, which aimed to estimate the impact of age on overdiagnosis of prostate cancer 15 years after screening stops, analyzed long-term follow-up data from the UK CAP (Cluster Randomised Trial of PSA Testing for Prostate cancer) trial, alongside English male mortality rates. Findings from the analysis were published by Brentnall et al in the International Journal of Cancer.
Analyzing data from more than 400,000 men as part of the CAP trial, the team compared the prostate cancer detection rate at screening (1.17%) with the difference in incidence 15 years post-screening (0.14%). They found that 11.7% of prostate cancers diagnosed at the one-off PSA screen would have remained undiagnosed for 15 years if the patients had been randomly assigned to the control arm (not invited for screening), and—importantly—if they would not die from other causes.
However, when competing mortality was factored in, the team found that the picture changed markedly by age:
- Men diagnosed at age 50 had a 16% chance that their cancer would never have been detected within 15 years.
- This rose to 32% for men diagnosed aged 70 and rose further to 58% for men diagnosed at age 80.
The findings suggest that prostate cancer screening and PSA testing is more appropriate for men in their 50s and early 60s, as there are likely to be low levels of overdiagnosis in this group.
Lead author Adam Brentnall, PhD, a Reader in Biostatistics at Queen Mary’s Wolfson Institute of Population Health, commented, “These findings suggest the need for more targeted, age-informed PSA testing or prostate cancer screening policies, including reexamining PSA testing policies in settings where they have led to high rates of opportunistic screening in older men….”
“This is because the current ‘PSA tests on demand’ health-care policy has led to high rates of opportunistic PSA testing in older men, who are at high risk of harms from overdiagnosis. These harms include unnecessary treatment—including surgery and radiotherapy—which carries significant side effects and can have a negative impact on the quality of life of men whose cancers would never have harmed them. In addition, screening men older than 70 years is also unlikely to confer benefit in terms of mortality reduction.”
The authors noted that there are some limitations to their analysis, including the fact that screening in the CAP trial was done before the use of magnetic resonance imaging targeted biopsy, which is expected to reduce overdiagnosis. Ongoing trials, including TRANSFORM and IMProVE, will help to provide additional evidence on overdiagnosis using contemporary screening protocols.
DISCLOSURE: For full disclosures of the study authors, visit onlinelibrary.wiley.com.
