Amid questions about how effective blood-based tests for prostate cancer might be, a new study suggests early screening with the test could identify about half of future deaths from the disease.
Updated: This post was updated to add comments from a co-vice chair of the U.S. Preventive Services Task Force (USPSTF).
Since the prostate specific antigen (PSA) test was approved by the Food and Drug Administration (FDA) in 1986, doctors and patients have relied on the results to identify men at highest risk of developing prostate cancer. But because prostate tumors can be slow to develop, studies have not supported the benefits of widespread, regular screening with PSA in reducing deaths from the disease. After a review of all the available evidence, last May the U.S. Preventive Services Task Force (USPSTF) recommended that men should skip routine PSA testing, due to the risks associated with the test, which can lead to biopsies and additional procedures that could cause complications such as pain, fever, bleeding, infection and incontinence.
But a new study published in the British Medical Journal from researchers at Memorial Sloan-Kettering Cancer Center in New York suggest that aside from men with a history of prostate cancer, other groups at high risk for the disease may be identified with a single PSA test when they are in their 40s.
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The researchers studied a population of 21,277 Swedish men aged 27 to 52 who were participating in the Malmö Preventive Project between 1974 and 1984. The men provided a blood sample at the start of the study and some of the men provided a second blood sample six years later, which the researchers analyzed for PSA levels.
Because there was little screening for prostate cancer in Sweden at the time of the trial, the researchers say their study could identify which men are most likely to benefit from PSA screening. By comparing PSA levels to later reports of prostate cancer diagnoses, they could determine how well PSA testing predicted later cancer, and death from that cancer. “Men at low risk of death from prostate cancer without screening have little to gain from being screened but still risk over diagnosis and over treatment; men likely to die from prostate cancer without screening could avoid cancer specific mortality if they choose to be screened,” the authors write.
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After analyzing the data, the researchers determined that men who were tested at age 45 received the most benefit in terms of learning their diagnosis and intervening with treatments. The same did not apply to men with a family history of prostate cancer, who should be tested more frequently for the disease due to their higher risk. The scientists say that testing at age 40 may not catch enough prostate tumors, which tend to develop with age, and that by the time a man reaches 50, aggressive tumors may have already taken hold, making them more difficult to treat.
Based on the results, the scientists found that men with a PSA level of 1.0 nanograms/milliliter or higher at age 45 had an above average risk of developing life-threatening prostate cancer. These men could benefit from more regular screening for changes in PSA levels until around age 70. For men whose PSA levels were below 1.0 nanograms/ml, the scientists suggest two additional tests, one during their early 50s and another at age 60 to make sure their PSA levels stay low.
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The practice would refine current recommendations, some of which call for no mass testing of men, and others that advise men to discuss with their doctors how often they feel comfortable getting tested. If followed, the researchers say their proposal “is likely to reduce the risk of over diagnosis while still enabling early cancer detection among those most likely to gain from early diagnosis. As such, a risk stratified approach to PSA screening will improve the ratio of its benefits and harms.”
Dr. Michael LeFevre, the co-vice chair of the USPSTF committee that advised against widespread screening using PSA, said in an email response to questions about the findings that at the time the task force made its recommendation, existing trials did not include men under age 50. Still, he wrote, “Men choosing to be screened should be informed of the potential for significant harm, and that the benefit demonstrated in the best studies is between small and none. Those who place a higher value on the possibility of benefit, however, small, than they do the well-established risk of harm may still choose to be screened. But we should not oversell the test based on hope, we should do the science that demonstrates that approaches other than that taken in existing trials minimizes the harms and increases the benefit.”
As recommendations about cancer screening continue to be refined, improved methods for identifying high risk individuals from the general population could lead to more focused, and effective, testing that can lower death rates from the disease.