Screening for prostate cancer with PSA testing has been shown to reduce death and the spread of prostate cancer. However, the PSA test remains controversial due to concerns of over-diagnosis and over-treatment. Clinicians and patients need smarter screening strategies to improve the accuracy of diagnosing lethal prostate cancer.
Researchers from Brigham and Women's Hospital and the Harvard T.H. Chan School of Public Health found that measuring PSA levels in younger men (between 40 and 59 years) could accurately predict a man's future risk of developing deadly prostate cancer later in life. Their findings indicate that a mid-life PSA could help identify men who are at greater risk of developing prostate cancer, and thus should be monitored more closely.
The study used data from the Physicians' Health Study, a randomized, placebo-controlled trial that tested aspirin and cardiovascular risk. The US male physicians who took part in the study provided blood specimens before the trial began in 1982. The study participants also filled out detailed questionnaires over the next 30 years.
The mid-life PSA study used information from 234 men who were diagnosed with prostate cancer, including 60 men who developed lethal prostate cancer, and 711 controls. All the men were between 40 and 59 years at the start of the trial. The research team measured PSA levels from the stored plasma samples and then followed the men's outcomes.
"We found a single baseline PSA-level measurement during midlife could accurately predict future risk of lethal prostate cancer. These data identify subgroups of men, based on their PSA levels at a given age, who could benefit from screening intervals tailored to their actual magnitude of risk."
– co-lead author Mark Preston, MD, MPH, a urologist
at Brigham and Women's Hospital
Predicting future risk
The single baseline PSA measured at mid-life accurately predicted future risk of prostate cancer for men in the study. Of the men with lethal prostate cancer, 82% occurred in men with a baseline PSA above the median at ages 40-49 years, 71% in men with a baseline PSA above the median at ages 50-54 years, and 86% in men with a baseline PSA above the median at ages 55-59.
The study also found that men at age 60 who had a PSA below the median (<1.0 ng/ml) were unlikely to develop lethal prostate cancer in the future.
"These data support the recommendation that risk-stratified screening for prostate cancer based on mid-life PSA should be considered in men aged 45 to 59," said senior author Lorelei Mucci, ScD, associate professor at Harvard T.H. Chan School of Public Health. "Our study does not imply prostate biopsy or definitive treatment is immediately required in younger men with higher PSA levels at baseline, as this could lead to over-diagnosis. Rather, these men should undergo more intensive PSA screening to enable earlier identification of cancer and potential cure while still possible."
The study's limitations include: the study population consists primarily of Caucasian men, there was a limited number of lethal events and an unknown number of participants may have undergone opportunistic screening prior to the study.
The study was published online ahead of print in Journal of Clinical Oncology on June 13, 2016.