What is the PSA screening controversy?
The goal of measuring PSA in men with no symptoms of cancer as a screening test for prostate cancer is to reduce the mortality caused by this cancer. However the utility of PSA as a screening tool for early detection of prostate cancer is subject to controversies over its ability to save lives.
Widespread use of PSA screening came into practice particularly in North America driven by the assumption that detecting prostate cancers earlier will allow for earlier treatment and thereby decrease mortality caused by this disease.
A substantial number of the cancers detected by PSA screening are low stage, and these patients will likely never die from this disease. PSA screening, due to its low specificity, does not allow differentiating between lethal and nonlethal types of cancers. Hence PSA systematic screening is inevitably associated with over-diagnosis and potentially overtreatment. Therefore, not only do these patients not benefit from early detection but they also carry the burden of a cancer diagnosis. In addition, a subset of these patients may suffer the side effects of an unnecessary treatment.
Despite the inconvenience caused by over-diagnosis and overtreatment, one may argue that PSA screening can still be considered successful if it improves disease-specific mortality in the population as a whole. Unfortunately, the conflicting results obtained from several randomized clinical trials specifically designed to evaluate the impact of PSA testing on prostate cancer mortality have not clarified the issue.
One large European trial (ERSPC) found that PSA screening significantly reduces the mortality (death rate) of prostate cancer but is also associated with a high risk of over-diagnosis. The cumulative incidence of prostate cancer was 8.2% in the PSA screening group and 4.8% in the control group. Patients in the screening group were 20% less likely to die from prostate cancer compared with the control group. The absolute risk difference between the two groups was 0.71 deaths per 1,000 men. This means that to prevent one death from prostate cancer, 1,410 men would need to be screened with PSA testing and 48 additional cases of prostate cancer would need to be treated.
Another trial (PLCO) conducted in the United States recently concluded that there is no evidence of an improvement in death rate from prostate cancer with annual PSA screening compared with usual medical care. After 13 years of follow-up, the cumulative mortality rates from prostate cancer in the intervention and control groups were 3.7 and 3.4 deaths per 10,000 person-years, respectively, meaning that there was no significant difference between the two groups.
Based on the results of the PLCO trial, the U.S. Preventive Service Task Force (USPSTF) advised against PSA screening in their draft recommendation issued in 2011. The USPSTF is in the process of updating the recommendation. Nevertheless, many experts continue to believe that not using PSA screening would result in the deaths of many men with curable prostate cancer. Nevertheless, many large, national urological associations (American Urological Association [AUA], Canadian Urological Association [CUA] and European Urological Association [EAU]) still value the benefit of PSA screening for men after age 45 to 50 and recommend physician-patient discussions about screening on an individual basis.
Early detection as through screening should still be offered. More than the over-diagnosis, the real challenge is to avoid overtreatment. Many patients with small, low-grade cancers may be candidates for active surveillance without treatment. This is why it is very important that men have an open and informed discussion with their doctor on the risks and benefits of prostate cancer screening before biopsy. In addition, the option of active surveillance instead of immediate treatment should always be discussed in case of newly diagnosed prostate cancer, if appropriate.
Despite the controversy of several recent publications and task force recommendations, the American Urological Association (AUA) still recommends the use of PSA for early prostate cancer detection. Early detection and risk assessment should be offered to men 40 years of age or older who wish to be screened. The fundamental principle of the AUA position is that knowing a man's baseline PSA values in his 40s to compare with future PSA tests could help identify those men with life-threatening prostate cancer at a time when there are many treatment options and cure is possible.
The American Cancer Society viewpoint regarding prostate cancer early detection is the recommendation that men have the chance to make an informed decision with their provider whether to be screened for prostate cancer. It is felt that this discussion should take place at age 50 years for men who are at average risk of having prostate cancer and are expected to live for 10 more years or longer. For men thought to be at high risk for prostate cancer, such as African-Americans and those men with first degree relatives (father, brother, son) with prostate cancer diagnosed at 65 years of age or younger, the age recommendation is 45 years of age and should be discussed starting at age 40 years for men at higher risk such as those with more than one first degree relative with prostate cancer diagnosed at a younger age. The frequency of PSA screening is recommended to be every two years for those men with a PSA < 2.5 ng/mL and yearly for those men with a PSA of 2.5 ng/ml.
The National Comprehensive Cancer Network (NCCN) guidelines for early detection of prostate cancer noted that most panel members favored prostate cancer screening, in men with 10 or more year life expectancy, beginning at age 45 years of age. The panel recommended testing at one- to two-year intervals for men with a PSA of > 1.0 ng/ml and every two to four years for those with PSA < 1 ng/mL.