Last week, the US Preventive Services Task Force (USPSTF) released new recommendations that men no longer undergo blood tests to measure levels of prostate-specific antigen (PSA), a protein produced by the prostate gland. These recommendations contradict the prostate cancer screening guidelines developed by Memorial Sloan-Kettering experts, which have been in place for about three years.
“We remain committed to our guidelines, which are based on years of careful studies and extensive review by our Medical Board,” says Howard I. Scher, Chief of the Genitourinary Oncology Service in Memorial Sloan-Kettering’s Department of Medicine.
The USPSTF concluded that there is “moderate or high certainty” that prostate cancer screening as currently conducted in the United States has no net benefit or that the harms resulting from screening outweigh the benefits. The group based its analysis on data that weighed the risks and benefits of conducting PSA tests and digital rectal exams on an annual basis starting at age 50 – or at age 45 for men at higher risk – which is the current practice of many physicians. The risks cited are due in large part to false-positive tests that result in unnecessary procedures and to treatment for cancers that are unlikely to become life-threatening.
“There is no doubt that prostate cancer screening can be associated with harm, mainly the risk of diagnosis and treatment of cancers that pose little risk to life or health, while the treatment carries immediate risks of harm to normal body functions,” Dr. Scher says. “But the answer is not to stop screening altogether; it’s to do so more intelligently.”
Memorial Sloan-Kettering experts concur with the recommendations against current screening practices in the United States. But they believe that the USPSTF has oversimplified the matter and did not take into account a more-selective and targeted approach to screening and treatment based on the assessment of the risk of having a clinically significant prostate cancer for each individual.
Evidence of the Benefits of Screening
Clinical trials have demonstrated that screening with PSA can reduce the risk of prostate cancer death by 20 to 44 percent over ten to 14 years when compared with not screening. Men who stand to benefit the most from early detection are those who are at high risk of dying from prostate cancer, including men with a family history of the disease, men with a genetic predisposition to prostate cancer, and African American men.
In addition to these risk factors, research carried out by Memorial Sloan-Kettering investigators has shown that a man’s PSA level between the ages of 45 and 60 is the most powerful predictor of his lifetime risk of developing a life-threatening prostate cancer or dying from the disease.
Rather than a uniform screening approach for the whole population, Memorial Sloan-Kettering guidelines recommend that men have an initial PSA test in their 40s, and that those at low-risk have testing less frequently, whereas men at intermediate to high risk have more frequent evaluations.
“Using this approach, the harms associated with overtreatment of low-risk cancer can be significantly or dramatically reduced by using an approach known as ‘active surveillance,’ or watchful waiting, which involves no immediate treatment but careful monitoring for changes in the cancer that show it has become more aggressive,” Dr. Scher says. “Definitive treatment of the prostate is only considered if it becomes measurably more threatening. We recommend that men found to have low-risk cancers strongly consider active surveillance rather than immediate therapy.”
“The mortality rate from prostate cancer in this country has declined steadily over the past 20 years with the widespread use of PSA testing,” Dr. Scher adds, “and the incidence of the disease and the mortality rate is likely to rise if testing substantially decreases.”