Prostate Cancer Screening: Don't Abandon DRE, Says Expert

Zosia Chustecka and Nick Mulcahy

September 14, 2015

UPDATED September 22, 2015 // Screening healthy men for prostate cancer remains controversial, but if the decision is taken to undergo such screening — after detailed discussion with the individual — then both a blood test for prostate-specific antigen (PSA) and a digital rectal examination (DRE) should be carried out, says a leading expert.

"Both PSA and DRE should be done," said David Penson, MD, MPH, chair of the Department of Urologic Surgery at Vanderbilt University Medical Center in Nashville, Tennessee.

Dr Penson was speaking in an interview as part of a campaign to raise awareness of Prostate Health Month in September. Medscape Medical News asked specifically about the role of DRE in screening for prostate cancer, as it has been dismissed as unnecessary by one physician group, the American Academy of Family Physicians (AAFP).

The issue has been highlighted in an awareness campaign headed by a prostate cancer patient Jody Gorran, who was diagnosed after an internist felt what he described as a hard nodule in his prostate during a DRE, even though PSA levels were below average. Gorran believes that his cancer would have been missed if he had not undergone the DRE, and is concerned for other patients who may be in a similar situation.

Recommendation Against Both PSA and DRE

The AAFP states that clinicians should not "routinely screen for prostate cancer using a prostate-specific antigen test or digital rectal exam." This recommendation appears in the Academy's third Choosing Wisely List issued in September 2013.

The AAFP continues: "There is convincing evidence that PSA-based screening leads to substantial overdiagnosis of prostate tumors. Many tumors will not harm patients, while the risks of treatment are significant. Physicians should not offer or order PSA screening unless they are prepared to engage in shared decision making that enables an informed choice by patients."

This recommendation echoes that from the US Preventive Services Task Force (USPSTF), which also recommends against routine screening for prostate cancer using the PSA test. But the USPSTF recommendations do not mention the DRE; this was specifically recommended against only by the AAFP.

So why did the AAFP add this extra recommendation?

For one thing, the DRE is even less specific and sensitive than the PSA test in detecting prostate cancer, said Reid Blackwelder, MD, board chair of the AAFP and professor of family medicine at East Tennessee State University in Kingsport.

"The DRE provides less information less consistently than PSA," he told Medscape Medical News. Both tests can lead to a harmful "cascade of testing."

The AAFP division that evaluates evidence and makes clinical preventive service recommendations felt that they should also advise against routine use of DRE, said Dr Blackwelder. The organization "doesn't just accept" what that USPSTF and other groups recommend, he pointed out.

Nevertheless, the DRE has been, in the past, part of the routine physical examination in primary care, he explained.

Even today, in working with residents, Dr Blackwelder sees that various parts of the physical exam, such as the DRE and breast exam, "are still being used as screening tools, despite a lack of evidence."

He explained that there is "too much variability" with DRE results: "Different clinicians will have different findings with the same patient." Also, there is no standard training for DRE.

 
If a patient has symptoms, then the DRE is an important test.
 

Furthermore, the DRE, when it does detect prostate cancer, is often not really working as a screening test, pointed out Dr Blackwelder, because patients who have a palpable cancer typically have symptoms. Thus, the DRE is a diagnostic test at that point, not a screening tool. "If a patient has symptoms, then the DRE is an important test," he said.

Strong evidence of benefit with DRE as a screening tool is just not there, said Dr Blackwelder, noting that in the landmark Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, men who had both a PSA and DRE did not have any reduction in morbidity or mortality.

Despite all of this, Dr Blackwelder emphasizes that the AAFP advises against "routine" use of the DRE and PSA, but he adds that there are exceptions to the recommendations. "Guidelines do not tell clinicians what they can and cannot do," he said. The screening recommendations apply to a general population. "But I treat the patient in front of me," said Dr Blackwelder.

"Do Not See Any Value in Screening"

From Dr Penson's point of view, the problem with both organizations (the AAFP and the USPSTF) is that "they do not see any value to any form of prostate cancer screening; they both have the same perspective."

"This perspective comes from their interpretation of the data," he commented. The data come from two large trials — the PLCO Cancer Screening Trial, which did not demonstrate any prostate cancer mortality reduction, and the ERSPC (European Randomized Study of Screening for Prostate Cancer), which did, and which continues to do so with updated data. The PLCO trial was seriously flawed in its control group, as many men in the "no screening" group actually underwent screening, as previously reported by Medscape Medical News.

The AAFP and the USPSTF have looked at these data, and even though there is evidence of benefit from the European trial, they have decided that any potential benefit is outweighed by potential harm, Dr Penson commented. "They fundamentally do not see any value to prostate cancer screening; that's their opinion," he emphasized, adding that it is this that he takes issue with. "They are not making their decision based on evidence. They are taking the data and then they are grafting their opinion onto it, so they are making the decision of what is right for the patient."

Quite a different stance is taken by the American Urological Association, which in its guidelines (on which Dr Penson was a coauthor) encourages urologists to talk to their patients about prostate cancer screening and to discuss the pros and cons and use decision aids to help the patient to understand the downside, as well as the upside, of such a screening, and then help each individual to make their own decision on what is best for them. "We went through the same process but we decided that it was the patient who should make the decision," he said. "This is not about populationwide screening, this is about it shared decision making and it is an individual decision."

Going back to the AAFP and USPSTF recommendations, he said: "Their position is that, yes, there is a benefit, but we think the harms outweigh the benefits, and so we don't think it should be recommended.... I have a very hard time accepting this as evidence-based because it is not, it's their opinion based on their interpretation of the data."

"I don't think that they are specifically against DRE, they are against prostate cancer screening altogether," he said. But he pointed out that the DRE can also detect other abnormalities, it can potentially palpate an anorectal cancer as well, so the recommendation against it has wider ramifications.

"It's been part of the physical exam for decades, and to throw it out now because 'we don't want to screen for prostate cancer'...well, where does this stop, maybe we shouldn't listen to hearts anymore," Dr Penson said with exasperation. The DRE is easy to do, and incurs no cost, as the patient is already seeing the doctor, so why not do it?

However, Dr Penson pointed out that some physicians are genuinely uncomfortable with performing a DRE, maybe that is an issue.

He also pointed out that both the United States and the European screening studies included DRE along with PSA testing: "They go together," he said.

The PSA test is more valuable, as the DRE is even less inexact than the PSA test, Dr Penson said, but "I do think that the DRE adds something to the PSA test." There are some data to support its utility in picking up prostate cancer, he continued, citing the Prostate Cancer Prevention Trial (PCPT), which was looking at finasteride for chemoprevention of prostate cancer.

Results from the initial report of the PCPT (N Engl J Med. 2003;349:215-224) show that in the placebo group of that trial, an abnormal DRE was found in about one out of five men, and very few of these also had elevated PSA levels (around 9440 men were randomized to placebo; 1977 had an abnormal DRE, and only 113 had an abnormal DRE and an elevated PSA level; data from Table 3).

Dr Penson also noted that the DRE picks up prostate cancer that is already palpable, which tends to be more advanced and more likely to need treatment.

There is a general agreement "that the PSA is an imperfect test," he said. "The DRE is also an imperfect test, but the two together actually offer more than either one alone," he said.

Editor's note: This article has been updated with an interview.

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