Federal Panel Discourages Use of PSA-Based Screening
Over the span of their lives, nearly 16% of American males will develop prostate cancer. For a large portion of cases, prostate cancer has a positive prognosis, while other cases are highly aggressive. The panel explains that the overall lifetime risk of dying from prostate cancer is 2.8%. The disease very rarely takes root before a male turns fifty years of age. Dying from the condition is extremely rare among men younger than 60 years of age. The greater majority of deaths occur when a man is at least aged 75.
Current screening methods for detecting prostate cancer include testing for serum PSA levels, a digital rectal exam, and/or ultrasonography.
According to the Task Force: "The evidence is convincing that PSA-based screening programs result in the detection of many cases of asymptomatic prostate cancer.”
If the detection process works, then what’s the problem? Well, there is also evidence that the majority of men who have “asymptomatic cancer” detected by PSA screening will have a tumor that meets histological criteria for prostate cancer. However, a tumor of this variety will either not progress or progress so slowly that it will have no impact on the man's lifespan or cause negative health effects, as he will likely die of another cause first.
The authors claim that it is very difficult to find out exactly how common overdiagnosis is with any form of screening and treatment program. The authors define overdiagnosis as the presence of the tumor, but the tumor does not progress to illness and/or death during a patient’s lifetime. The more instances of prostate diagnosis there are, the higher the rate of overdiagnosis. One study found as many as 25% of men were diagnosed with prostate cancer following PSA screening and biopsy. The authors add that overdiagnosis is much more likely among older patients with shorter life expectancies.
The Task Force’s primary goal was to determine prostate cancer mortality in all prostate cancer screening studies. The aim of any form of cancer screening is to minimize death rates. For males up to seventy years of age, it is clear that screening does not reduce death rates from prostate cancer. And for men between the ages of 50 and 69 years of age, there is compelling evidence that following screening the reduction in mortality is slim to none.
The authors divided prostate cancer found by screening into three categories.
1. Patients who died regardless of early diagnosis and intervention.
2. Patients who improved their life expectancy due to early diagnosis and intervention.
3. Patients who had positive outcomes, regardless of whether or not they had screenings, due to indolent tumors progressing slowly.
Of all the males who were detected to have prostate cancer as a result of a PSA test, 95% did not die as a result of that cancer – this data also includes those individuals who received no form of treatment. Not a single study has found that screen-detected prostate cancer has caused a drop in death rates.
These tests can lead to harmful outcomes due to follow up care. Studies have found that nearly 90% of patients with PSA-detected prostate cancer go for treatment right away. Such treatments can include radiotherapy, surgery or androgen deprivation therapy. Of 1,000 men who undergo prostate cancer surgery, as many as 5 die in a month and between 10 and 70 experience serious complications but survive the ordeal.
The authors conclude that men who are overdiagnosed gain no benefit from intervention but are still subjected to all the related risks of surgery, radiation, or hormone therapy. As a result, overtreatment is a critical consequence of PSA-related screening as it is currently used, especially in the context of a high likeliness for physicians and patients to elect treatment for most instances of screen-detected cancer.
However, not all medical experts are convinced this recommendation is sound advice. Phillip Kantoff, MD, director of the Dana-Faber’s Lank Center for Genitourinary Oncology in Boston, Massachusetts, claims, “This is the wrong message at this point in time. The whole issue of PSA-based screening is complex. It involves multiple steps and multiple decision points. The blanket statement saying that PSA-based screening is of no value is the wrong message right now.
Dr. Kantoff adds, “There is no question that we need to be more careful with whom we screen, and we recognize that not every man needs to be screened.” He acknowledges that the PSA test has specificity and sensitivity issues, but he claims that it still has merit as a screening tool when used appropriately.
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