PSA prostate screening test does more harm than good says government panel
Since the 1990s, the prostate specific antigen (PSA) test has been used routinely to screen men for prostate cancer. However, several years ago, the US Preventive Services Task Force (USPSTF) began questioning the benefits versus risks of the test. On May 21, they finalized the position; their results were published online on May 22 in the Annals of Internal Medicine.
The task force noted that they had reviewed new evidence on the benefits and harms of PSA–based screening for prostate cancer, as well as the benefits and harms of treatment of localized prostate cancer. They concluded that “there is moderate certainty that the benefits of PSA-based screening do not outweigh the harms.” The assigned the PSA test a “D” rating, which signifies that “there is moderate or high certainty that the service has no benefit or that the harms outweigh the benefits.” Before the release of the new recommendations, the USPSTF graded the screening as a “C” for men under 75, which meant that there is at least moderate certainty that the overall net benefit of screening is small. The guideline is not a mandate. The USPSTF stresses that men who want a PSA test still can get one; however, only after a physician explains the uncertainties.
In an editorial published with the guideline in Annals of Internal Medicine, some urologists countered that the task force underestimated PSA's value and overestimated its harms. “What PSA screening offers the men is a substantial opportunity to avoid dying a particularly unpleasant death from prostate cancer,” noted the editorial’s co-author Dr. William Catalona of Northwestern University, who pioneered the testing. He spoke Monday from a meeting of the American Urological Association, where physicians debated the guideline's impact. The urology association advises that men be informed of the potential risks and benefits before screening.
The American Cancer Society (ACS) is in favor of the USPSTF recommendations. ACS Chief Medical Officer Dr. Otis Brawley, noted that he hoped it would help deter mass screenings, where men are given free PSAs at shopping malls and sports arenas without being told of the controversy. He claims that these screenings are “big business” when health centers profit from the follow-up care.
The panel noted that convincing evidence exists that the number of men who avoid dying of prostate cancer because of screening after 10 to 14 years is, at best, very small. Two major trials of PSA screening were reviewed by the USPSTF: the U.S. PLCO (Prostate, Lung, Colorectal, and Ovarian) Cancer Screening Trial and the ERSPC (European Randomized Study of Screening for Prostate Cancer). The U.S. trial did not demonstrate any prostate cancer mortality reduction. The European trial found a reduction in prostate cancer deaths of approximately 1 death per 1,000 men screened in a subgroup of men aged 55 to 69 years. The panel concluded that there is adequate evidence that the benefit of PSA screening and early treatment ranges from 0 to 1 prostate cancer deaths avoided per 1,000 men screened.
The USPSTF noted that convincing evidence demonstrates that the PSA test often produces false-positive results (approximately 80% of positive PSA test results are false-positive when cutoffs between 2.5 and 4.0 μg/L are used) (A false-positive test is one that falsely suggests that an cancer is present.) In addition to the distress the results cause the patient, these men are more likely to have additional testing, including one or more biopsies, in the following year than those who have a negative test result (5). New evidence from a randomized trial of treatment of screen-detected cancer reported that approximately one third of men who undergo a prostate biopsy experience pain, fever, bleeding, infection, transient urinary difficulties, or other issues requiring clinician follow-up; approximately 1% of these men require hospitalization.
The USPSTF noted that significant evidence exists that almost 90% of men with PSA-detected prostate cancer in the United States have early treatment with surgery, radiation, or androgen deprivation therapy. Furthermore, up to 5 in 1,000 men will die within one month of prostate cancer surgery and between 10 and 70 men will survive but suffer serious complications. The panel notes that radiotherapy and surgery may result in long-term adverse effects, including urinary incontinence and erectile dysfunction in at least 200 to 300 of 1,000 men treated with these therapies. Radiotherapy is also associated with bowel dysfunction. The USPSTF notes that androgen deprivation therapy has not been shown to improve survival in localized prostate cancer. Furthermore, the therapy is associated with erectile dysfunction (in approximately 400 of 1,000 men treated), as well as gynecomastia (enlarged breasts) and hot flashes.
The panel noted that convincing evidence exists that PSA-based screening leads to substantial overdiagnosis of prostate tumors. They note that the amount of overdiagnosis of prostate cancer is a major concern because a man with cancer that would remain asymptomatic for the remainder of his life cannot benefit from screening or treatment. Because it is difficult to determine whether an early cancer will progress to a lethal stage or remain indolent, both physicians and patients opt for treatment; thus, many men are being subjected to the harms of treatment of prostate cancer that will never become symptomatic. The panel concluded that convincing evidence exists that PSA-based screening for prostate cancer results in considerable overtreatment and its associated harms.
Reference: Annals of Internal Medicine