One in eight undergoing repeated PSA screening receive false-positive result
MedWire News: Every eighth man undergoing repeated prostate-specific antigen (PSA) screening will have at least one false-positive (FP) result, show findings from the Finnish component of the European Randomized Study of Screening for Prostate Cancer.
Of concern, the researchers report that “more than a quarter of men with FP results are subsequently diagnosed with prostate cancer”, yet they also found these patients are at high risk for dropping out of further screening.
“Our findings indicate an increased risk for future prostate cancer with a history of one or several FP results,” write TP Kilpelainen, from the University of Tampere, and colleagues.
From three 4-yearly PSA screening rounds over an average 9.2 years, where a measurement of more than 4 ng/ml prompted referral for further diagnostic examinations, 1611 cancers were detected among 10,327 men.
A FP result was defined as a positive PSA test result without subsequent histopathologic confirmation of prostate cancer diagnosis within 1 year.
For men who underwent all three screening rounds, there was an overall risk for receiving at least one FP result of 11.6%. Men who underwent at least one screening round had a 6.4% risk for a FP result in the first screening round, 8.0% in the second, and 7.8% in the third.
The risk for a prostate cancer diagnosis after a FP result was 12.3–19.7% during the next round of screening, compared with 1.4–3.7% following a negative screening result. Among 128 men who were diagnosed with prostate cancer after a FP result in the first round, 78.1% had low-grade tumors.
Importantly, men with a FP result were 1.5–2.0 times more likely not to participate in subsequent screening rounds compared with men with normal screening results.
The research highlights the paradox that FP men frequently have persistently high PSA levels, undergo several negative biopsies, yet are overall more likely to be diagnosed with prostate cancer, write Kilpelainen and co-authors in the British Journal of Cancer.
“New approaches are urgently needed… to predict which [FP men] may harbor a clinically significant prostate cancer, which may have an insignificant indolent prostate cancer, and which may have other factors underlying the elevated PSA level,” the team concludes.
Julietta Patnick, director of the UK’s NHS Cancer Screening Programmes, said: “False positives are an issue for any screening program, and this Finnish paper is very helpful at gaining an understanding of how they might figure in the context of prostate screening.”
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By Sarah Guy