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Psa guideline exercise
1. Developing Clinical Guidelines: An Introductory Exercise John Voss, MD Andrew Wolf, MD Division of General Medicine University of Virginia School of Medicine Charlottesville, VA Some rights reserved under the creative commons license. For information please contact jv4w@virginia.edu
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5. 2009 Prostate Cancer Incidence & Mortality Insert text box about lifetime and yearly probability of diagnosis and death from prostate cancer Slide data drawn from Cancer Statistics 2009. CA Cancer J Clin 2009;59:225-49.
Hello, my name is John Voss and I’m Andy Wolf. We are general internists on the faculty of the University of Virginia School of Medicine. Today we have a brief exercise for you on guldeline development. Guidelines are an important method for promoting consistently high quality, evidence-based care, but not all guidelines are created equal. Today we’ll talk about the requirements for guidelines and give you a chance to try writing a guideline of your own. After this session, we’ll regroup to compare your ideas about a guideline for prostate cancer screening and talk about how the latest American cancer society guideline for prostate cancer screening was developed.
At the conclusion of this exercise, we expect that you will be able to 1. Describe the components of an effective guideline 2. Describe the tasks and some of the pitfalls involved developing clinical guidelines
For purposes of this exercise, lets imaging that you are are a general internist working in a multispeciality practice group. The senior administrator for your group knows of your interest in quality and has asked you to develop a guideline about using PSA testing for prostate cancer screening because there seems to be uncertainty among physicians and patients about the best use of this test.
To help you create this guideline we’ve assembled some useful information. In the next few slides we will Summarize the conditions necessary for developing and conducting effective screening programs Review the basic epidemiology of prostate cancer in North American men. Summarize the two best prospective studies about PSA screening. Please use this information to formulate a guideline for the use of PSA testing to screen men for prostate cancer. You have one hour to review these slides and create a 2-3 sentence draft guideline. At the conclusion of this exercise two groups will be selected to describe their guideline and the justification for its conclusions. Keep in mind that in real life, developing a guideline we’ve asked you to create could take weeks or months of work. We only expect a good faith effort in the time allotted to do the best work that you can.
In this figure of the incidence of prostate cancer over time, from 1975 to 2006, you can see what happens when a new screening test – in this case the PSA - is widely adopted in the population – the incidence of prostate cancer skyrocketed after its introduction around 1990, and then plateau’d as repeat screening detected fewer & fewer new cases. You can also see that within a year or two of widespread PSA testing, the mortality rate from prostate cancer began to fall, and continues to decline. Many advocates of PSA screening cite this association as evidence of benefit, while others observe that the decline began too soon after PSA screening was initiated to ascribe it to the PSA. They claim that other factors, such as improved treatment of advanced disease, may be playing a greater role in the mortality decline.
Before we go further, let’s define what we mean by screening. In screening progams we want to identify asymptomatic patients who may have early stage disease. When we use tests to diagnose the cause of a specific symptom we have moved beyond screening. Using a PSA test to detect cancer in asymptomatic men is screening. Using the same test to attempt to rule out metastatic prostate cancer in a middle aged man with back pain is not screening.
The criteria for an effective screening program are well established. To warrant screeing… read slide.
Heres some basic information about PSA test and some prostate cancer treatments. Studies of the PSA test characteristics show significant variability. Recall that tests with low sensitivity will fail to detect disease and tests will low specificity will have many false positives. The PPV is around 30% in most studies, meaning that patients 3 of 10 patients with an abnormal PSA can be expected to have prostate cancer. The test is not terribly expensive but the cost of a diagnostic biopsy and treatment are significant.
Surgery and radiation therapy for prostate cancer are low mortality treatments, but patients often suffer distressing side effects. This slide illustrates the prevalence of side effects in men one year after treatment. Side effects may be lower at highly specialized prostate cancer treatment centers.
The most significant development in prostate cancer screening over the past several decades was the publication of two back-to-back randomized trials of screening last year in the New England Journal of Medicine. One from the U.S. and the other from Europe. The U.S. trial represented the prostate arm of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (or PLCO for short).
The PLCO randomized 73,000 U.S. men to annual screening with the PSA and digital rectal exam over about 5 years, and then followed them for about a decade.
Not surprisingly, more men in the screening arm of the PLCO – depicted by the black line -- were diagnosed with prostate cancer compared with those in the “usual care” control arm, shown in red.
As you can see, the greater detection of prostate cancer among those in the screening arm did not translate into a reduction in prostate cancer-specific mortality: there was no significant difference in mortality between the 2 arms.
Although there was no benefit to screening demonstrated by the PLCO trial, there were some major problems with the study which likely contributed to the negative result. First, the contamination rate was extremely high: slightly more than half of the control subjects underwent screening during the study. Second, many men in both arms of the study had been screened prior to study entry. Hence, the study population was at reduced risk of developing prostate cancer, since many “prevalent” cases had been removed. Third, fewer than 50% of men with positive screening tests ended up getting a prostate biopsy; thus, many men who probably had prostate cancer were never diagnosed and treated. For all of these reasons, it would have been very difficult for the PLCO to have demonstrated a benefit to screening if such a benefit, in fact, exists.
The other randomized trial, published simultaneously, was the European Randomized Study of Prostate Cancer or ERSPC.
The ERSPC trial randomized over 160,000 men from 7 European countries to screening with the PSA alone, between every 2 and every 4 years, again followed them out for about a decade.
In the ERSPC, a statistically significant reduction in prostate cancer mortality was observed: the relative risk of prostate cancer death? in the treatment arm (depicted here in blue) was 0.8, compared with the control arm depicted in red, a 20% mortality difference, which emerged about 10 years after screening was initiated. This study was a “purer” experiment, in that contamination rates were very low (only about 6% of the control group underwent screening) and pre-trial screening rates were also very low.
The main problem with the ERSPC was with the absolute risk reduction conferred by screening. Over 1000 men needed to be screened and 48 men needed to be treated to prevent one death from prostate cancer over 10 years. This means that 47 men were treated but did not benefit in terms of life prolongation, at least over a ten year period. This problem of overdiagnosis and overtreatment is believed to be greater for prostate cancer than for any other cancer for which screening is offered.
Read slide As you discuss these issues, keep in mind that reasonable people can disagree. If you have trouble, think about whether the difficulties you are having reflect differences in how you seek to balance the potentially competing interests of patients, physicians, insurers and society. Good luck developing your guideline!
In the ERSPC, a statistically significant reduction in prostate cancer mortality was observed: the relative risk of prostate cancer death? in the treatment arm (depicted here in blue) was 0.8, compared with the control arm depicted in red, a 20% mortality difference, which emerged about 10 years after screening was initiated. This study was a “purer” experiment, in that contamination rates were very low (only about 6% of the control group underwent screening) and pre-trial screening rates were also very low.
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