September 08, 2015
Prostate cancer is the most common cancer in American men behind skin cancer. There are expected to be 220,800 new cases diagnosed in the US this year. Although this number is high, death rates from prostate cancer are relatively low. Almost 100% of men diagnosed with the disease will survive 5 years or more - a rate many medical professionals attribute to prostate-specific antigen testing.
The US Food And Drug Administration (FDA) first approved prostate-specific antigen (PSA) testing to screen asymptomatic men for prostate cancer in the early 1990s. In the decade prior to this approval, 5-year survival rates from the cancer stood at around 70-75%. By 1998, it had increased to 98.2%.
Although some health care experts have hailed PSA testing as the best available method to screen men for prostate cancer, there has been long-standing debate surrounding its use in routine testing.
PSA testing can lead to many false-positive results, meaning men can be alerted to cancers that are not actually present. Furthermore, critics argue that the test can lead to overdiagnosis, causing many men to undergo treatment they do not need.
September is National Prostate Cancer Awareness Month. In line with this campaign, we look at the evidence for and against PSA testing for prostate cancer and ask: should it be used for routine prostate cancer screening?
Questioning the accuracy of PSA testing
PSA is a substance made by cells in the prostate gland. During a PSA test, a clinician will take blood from the patient and send the sample off to a laboratory, where levels of PSA are measured by nanograms per milliliter (ng/mL).
High levels of PSA - usually 4.0 ng/mL or higher - can indicate the presence of prostate cancer, and a man with such levels is likely to need a biopsy to determine whether he has the cancer.
However, high PSA levels can also be a sign of less harmful conditions, such as prostatitis - inflammation or infection of the prostate gland - or enlarged prostate, a condition that can cause urination and bladder problems. Furthermore, the PSA test is unable to determine the difference between aggressive and benign prostate cancers. This is where concerns about the test's accuracy come into play.
Past research has estimated that between 17-50% of men diagnosed with prostate cancer through PSA testing have tumors that would not have resulted in symptoms throughout their lifetime.
This means many men may receive treatment for prostate cancer - such as surgery, radiation or hormone therapy - that they do not need, which can lead to serious side effects, including urinary incontinence and erectile dysfunction.
Recommendations against PSA testing met with criticism
Such factors have fueled recommendations against routine prostate cancer screening. In 2012, the US Preventive Services Task Force (USPSTF) led the way by issuing a recommendation against PSA-based screening for prostate cancer for men of all ages who do not have symptoms.
USPSTF co-chair Dr. Micheal Lefevre said of the recommendation:
"Prostate cancer is a serious health problem that affects thousands of men and their families. But before getting a PSA test, all men deserve to know what the science tells us about PSA screening: there is a very small potential benefit and significant potential harms.
We encourage clinicians to consider this evidence and not screen their patients with a PSA test unless the individual being screened understands what is known about PSA screening and makes the personal decision that even a small possibility of benefit outweighs the known risk of harms."
The move was met with much criticism. In a response published in the Annals of Internal Medicine, a group of prostate cancer experts stated that, given the fact that prostate cancer does not often present symptoms in its early stages, "eliminating reimbursement for PSA testing would take us back to an era when prostate cancer was often discovered at advanced and incurable stages."
This statement was echoed in another study by researchers from the University of Rochester Medical Center in New York, NY, which estimated that without routine PSA testing, an additional 17,000 men every year will likely be diagnosed with prostate cancer in its advanced stages.
Despite such criticism, other organizations - including the Centers for Disease Control and Prevention (CDC) - support the USPSTF's recommendation.
Though not explicitly backing the USPSTF recommendation, the American Cancer Society do not provide guidelines that back routine PSA testing for prostate cancer. Instead, they state that "men have a chance to make an informed decision with their health care provider about whether to be screened for prostate cancer."
They say a patient's discussion with their health care provider about prostate cancer screening should start at age 50 for men who are at average risk of the disease and who are expected to live 10 years or more, while the discussion should take place at age 40 for men at high risk of prostate cancer.
The American Urological Association and the American College of Physicians have similar recommendations.
Does PSA testing reduce prostate cancer mortality?
But despite recommendations against routine prostate cancer screening for men with no symptoms, many health care professionals believe PSA testing is crucial for preventing deaths against the disease.
In a report by The Wall Street Journal, Dr. Oliver Sartor, medical director of the Tulane Cancer Center in New Orleans, LA, said:
"Since PSA screening became routine in the 1990s, prostate-cancer mortality rates have declined by nearly 40%. I think PSA testing is the most likely explanation."
He pointed to the aforementioned study estimating that, without routine PSA testing, an additional 17,000 men every year would be diagnosed with advanced prostate cancer. "We know that not all these men would be cured if detected earlier," he added, "but PSA testing dramatically improves the odds that prostate cancer will be found before it becomes incurable."
And support for PSA testing is not only coming from health care experts. Meg Burgess, a specialist nurse for Prostate Cancer UK, told Medical News Today:
"Many men with prostate cancer feel that having a PSA test meant their cancer was diagnosed at a stage when it could be treated, and they would like all men to be able to benefit like they feel they have. As a result there have been calls for a screening program for prostate cancer using the PSA test to be introduced."
In August 2014, we reported on the long-term results of the European Randomised Study of Screening Prostate Cancer (ERSPC), launched in 2003 to determine the effect of routine testing on prostate cancer death rates.
The study, which involved more than 162,000 men aged 50-74 from eight countries, revealed that over 13 years of follow-up, routine PSA testing reduced the number of prostate cancer deaths by 21%. In addition, men who were screened had a lower risk of developing advanced prostate cancer and a 27% reduced risk of death from the disease.
- More than 2.5 million men in the US are living with prostate cancer
- Around 1 in 7 men will be diagnosed with prostate cancer in their lifetime
- Prostate cancer is most common in older men, with 6 in 10 cases occurring in men over the age of 65.
Study leader Prof. Fritz Schröder said the results indicate that PSA screening "delivers a substantial reduction in prostate cancer deaths, similar or greater than that reported in screening for breast cancer."
However, even Prof. Schröder noted that routine screening can lead to overdiagnosis in around 40% of cases, which can lead to overtreatment and common side effects. As a result, he concluded that "the time for population-based screening has not arrived."
The results of another study - the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial - found that between 1993 and 2001, PSA-based screening for prostate cancer appeared to have no mortality benefits compared with a digital rectal examination.
With such conflicting studies on PSA testing for prostate cancer, it is no wonder that health organizations appear to be sitting on the fence when it comes to recommendations for such screening.
The CDC, who say they support the USPSTF recommendation against PSA screening for prostate cancer, informed MNT they also support "informed decision-making" about PSA screening.
Dr. Otis Brawley, chief medical officer at the American Cancer Society, told MNT that the majority of individuals are unaware of what the current recommendations are when it comes to prostate cancer screening.
"Virtually every organization recommends men be informed of the documented harms and potential benefits of screening and be allowed to make a decision about being screened," he added. "Some may reasonably choose screening and make the decision about treatment after diagnosis. Even the USPSTF statement - which starts out recommending against routine screening - is consistent [with this]."
Identifying new biomarkers, diagnostics for prostate cancer is important
By looking at all available evidence for and against PSA testing for prostate cancer screening, it seems impossible to reach a firm conclusion about whether the test should be routinely offered to men or not.
Many medical experts believe that if the test could distinguish between aggressive and harmless prostate cancers, routine screening would not be an issue as the risk of overtreatment would be reduced. But of course, more research is needed to reach this point.
Aside from PSA testing, many health care professionals believe more research is needed to identify new screening strategies for prostate cancer.
"Research into new biomarkers and diagnostic investigations to better diagnose significant prostate cancer and prevent the overdiagnosis of insignificant disease is important, as well as research to identify who is most at risk of getting the life-threatening form of the disease," Burgess told MNT.
She added that Prostate Cancer UK are in the process of developing "an accurate and reliable test for the disease that can be delivered through primary care at a reasonable cost in order for it to be used widely and benefit as many men as possible."
Dr. Djenaba Joseph, of the Division of Cancer Prevention and Control at the CDC, also believes we need better ways to screen for prostate cancer. But she told MNT that "until we make these discoveries, and even when we do, men and their families should turn to trusted health care professionals to help them make informed decisions."
Written by Honor Whiteman