The recommendation to perform PSA (prostate-specific antigen) tests on all men over 50 years of age for screening or early detection of prostate cancer is increasingly being questioned. This marker, which has been used in clinical practice for more than 20 years, has become a routine test in the consultations of family physicians and urologists. However, despite its widespread use, the recent appearance of several publications, the most recent by the US Preventive Services Task Force (USPSTF), reopens the debate on its use.
Why should early diagnosis of prostate cancer be performed or not?
There are a number of reasons in favor of early diagnosis. Undoubtedly, the most significant is that prostate cancer is the most common tumor in men, and that early treatment of the tumor increases survival. As a note, 9% of men over 50 years of age will suffer from prostate cancer (PCa), but only 3% will die as a result of it. In order to detect it early, a digital rectal examination is recommended, especially PSA. Before the PSA era, only 30% of tumors were diagnosed at an early stage, i.e. they were localized and potentially curable tumors. Since the introduction of PSA these percentages have changed radically, and now most tumors are diagnosed when they are localized.
The downside is that many patients undergo unnecessary prostate biopsies without even having a tumor, and of those who do, 50% have no clinical relevance, i.e. they are overdiagnosed and overtreated. This implies the likelihood of side effects as a consequence of treatment, especially two; impotence and incontinence, in a considerable percentage of patients with a tumor with a good prognosis who will not die whether they are treated or not. Therefore, the main disadvantages of PSA are that it is not a specific marker of prostate cancer, and that it does not allow differentiation between aggressive tumors, which can risk the patient’s life, and those that are not.
Does PSA quantification reduce mortality in PCa?
Despite the wide use of PSA and the countless publications in the scientific literature, we did not have direct evidence to prove the early diagnosis of prostate cancer. For this, long-term examinations were needed (more than a decade of follow-up) with a large number of patients, in which mortality due to PCa was compared in patients who had undergone screening or early diagnosis versus patients who had not (control group). In 2009 two studies were published, one American (PLCO) with nearly 80,000 patients and the other European (ERSPC) with more than 150,000 patients, which sought to answer this question. However, the results have not definitively clarified the situation.
Thus, the American study found no difference in survival between the two groups, although, critically, 40% of the patients in the control group had undergone PSA testing at some point, so this “contamination bias” casts doubt on the authenticity of the results. The European study, with more patients, does indicate, at 9 years of follow-up, a 20% decrease in the risk of dying from PCa. However, to prevent one death from PCa, it was necessary to test 1,410 men and diagnose and treat 48. As an example, in breast cancer, to prevent one death, it is essential to test 1,000 women and diagnose and treat 10.
Why continue to use PSA?
Despite the doubts, PSA continues to be the most effective test available for detecting prostate cancer and for its follow-up when it has already been diagnosed. The key lies in its rational use, in how and from whom to request it, and in an appropriate interpretation of its values. Its generalization has led to the systematic determination of all men who come to a consultation, regardless of their age, and without specifying the dangers and benefits of such analysis. The ideal is to explain to the patient the objectives of its quantification, with its pros and cons and, if it is determined, to rationalize its use. Thus, for example, it should not be performed or should not be determined in men over 70 or 75 years of age, or in any case in patients with a life expectancy of less than 10 years, since in these cases the advantages of detecting a tumor are few.
Nor is it necessary in many cases to quantify it every year, given that in patients who have values of less than one the risk of developing a tumor is practically nil. Therefore, while waiting for a better marker or test to appear, PSA will continue to be used, the key is to perform it well.