An updated Cochrane review suggests that prostate cancer screening using blood tests may reduce disease-specific mortality, reversing the conclusions of the previous review.
The findings could add further weight to the debate over the value of prostate cancer screening, a controversy that has persisted for more than a decade, and may support the case for early detection strategies.
The previous review, based on a meta-analysis of five RCTs, was the backbone of decisions not to introduce national screening programmes in a number of countries.
In November, the UK National Screening Committee (NSC) declined to endorse widespread population screening for prostate cancer, although it proposed offering a targeted screening programme for men with confirmed BRCA1 and BRCA2 gene mutations. [see earlier story here].
“Since then, results from two new, large trials have become available, alongside extended follow-up data from previously included trials,” the review authors noted. “Thus, an update was warranted.”
The updated review found “modest benefits” from screening. This did not reflect a change in the underlying evidence, but rather the longer follow-up periods now available, which enabled detection of a mortality benefit that was not visible earlier.
The review team analysed data from six trials, involving nearly 800,000 people across Europe and North America. They found that screening with a PSA blood test reduced prostate cancer deaths by roughly two for every 1,000 men screened.
The mortality data comes from a trial that followed 162,241 men for 23 years.
“With new data now available, we can now say with moderate certainty that PSA screening reduces prostate cancer deaths in men with a sufficient life expectancy,” Dr Philipp Dahm, the report’s senior author from the University of Minnesota, said in a statement.
“This suggests that for the right patient – someone who is well-informed, has a good life expectancy, and understands the full implications of screening – there is now a reasonable evidence base to support a conversation about PSA screening.
“This represents an important change in the evidence for future guideline developers and policy makers to consider.”
Overdiagnosis still an issue
Experts have long debated whether the benefits of early detection through screening outweigh the risks of overdiagnosis and overtreatment.
The authors of the updated Cochrane review emphasised that the potential for overdiagnosis “still remains a key issue”.
They noted that screening detected an estimated 30% more prostate cancers overall, mostly at an earlier stage, with roughly 36 additional cancers diagnosed per thousand men screened for every one to two deaths prevented.
Because PSA testing can identify low-grade cancers that may never have caused symptoms or harms during a patient’s lifetime, screening can cause anxiety and lead to unecessary treatment.
“We want to be clear that this is not a blanket endorsement of universal screening,” Dr Franco said, adding that patients and doctors should make decisions jointly that balance the risks and benefits of testing.
The review also did not address impacts on quality of life, such as complications from biopsies, sexual dysfunction and urinary problems, although the authors said evidence from other studies should be taken into account by policymakers.
At the same time, newer approaches aimed at reduce the potential harms from screening, such as MRI and active surveillance, are continuing to evolve.
The updated review examined a newer generation of screening tools combining PSA testing with a kallikrein panel blood test and MRI scanning, which aim to achieve greater precision and reduce unnecessary biopsies.
“We found insufficient evidence on the potential harms of screening, such as biopsy- and treatment-related complications,” the authors noted.
“Emerging alternatives, such as screening with a kallikrein panel and MRI, may have little to no effect on diagnoses of prostate cancer, but the results on mortality are not yet known”.
The full updated review is published in the Cochrane Library [link here].