Difference between revisions of "Sandbox"

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Judging Statistics
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An Older Look at PSA Screening
 
From [http://www.nytimes.com/2009/03/28/us/28judges.html?_r=1&hp the ''New York Times''] comes this triumph of statistics.  The graphic below summarizes why foul play was suspected in Luzerne County, PA on the part of two greedy judges who lacked a moral compass.
 
 
<center>http://www.dartmouth.edu/~chance/forwiki/CB461.gif</center>
 
  
Discussion:
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[http://chance.dartmouth.edu/chancewiki/index.php/Chance_News_46#Does_a_screening_test_do_more_harm_than_good A previous wiki] succinctly discussed the two recent large studies—77,000 in the U.S. and 182,000 in Europe—regarding prostate cancer and the efficacy of PSA screening.  Nevertheless, [http://www.scientificexploration.org/journal/reviews/reviews_11_2_alper_3.pdf some history] might be useful.  Back in the late 1990s a major issue was the treatment effectiveness of radioactive seed implantation, SI, as compared to the supposed “gold standard” of radical prostatectomy, RP.  Because prostate cancer is slow growing, urologists insisted that seven years since the inception of SI treatments was not enough data because more time was needed to properly compare the two treatments.  This issue has largely been resolved in the ensuing decade to the point where urologists no longer invoke the phrase gold standard and now offer either SI or RP to their patients.
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1. Why is the graph so incriminating?
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The PSA test was originally conceived as a monitoring method to judge the condition of those who were already diagnosed with prostate cancer, as opposed to acting as a screening test to determine if prostate cancer was present. Like many blood tests, it is merely an indicator; for the PSA test particularly, the result can vary according to the size of the gland, presence of infection or inflammation, how recently an ejaculation occurred, and, of course, whether cancer is present.  Men started to demand the PSA and an expensive industry took off precisely because of the plausible, but ultimately empirically unwarranted belief that prompt intervention promoted the saving of lives. 
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2However, many statistics textbooks caution, "The data never speaks for itself." What possible mitigating facts regarding variability are missing?
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However, even back then it was suspected that whatever the treatment,—SI, RP, cryotherapy, watchful waiting, electron beam radiation—the mortality rate was more or less the sameSaid another way, (mass) “screening” as opposed to “testing” was of doubtful value because if the prostate cancer was indolent the patient would die with it rather than of it, and if the prostate cancer was aggressive, none of the treatments would do much good. 
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3. As interesting as the statistical data is, read the article itself as well as [http://www.nytimes.com/interactive/2009/03/28/us/20090328_JUDGES.html the audios of victims] to see the non-statistical evidence unearthed by the prosecutionWhich do you find more compelling?
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Discussion
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Submitted by Paul Alper
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1. One often hears the term, “five-year survival rate.”  Some researchers consider this term completely misleading especially when applied to prostate cancer treatments.  What is misleading about it?  Why is mortality rate a better way of comparing treatments?
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2. Consider the following statement: “The U.S. Preventive Services Task Force (USPSTF) concludes that the evidence is insufficient to recommend for or against screening asymptomatic persons for lung cancer with either low dose computerized tomography (LDCT), chest x-ray (CXR), sputum cytology, or a combination of these tests.”  Go to [http://www.ahrq.gov/clinic/3rduspstf/lungcancer/lungcanrs.htm here] for the rational.  How does this accord with screening for prostate cancer?
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3. Find a friendly librarian to determine the percentage of watchful waiting treatment of prostate cancer in western European countries compared to the U.S.  Do likewise for RP and SIAssuming that RP is the most aggressive and watchful waiting the least aggressive, where does the United States stand?

Revision as of 17:35, 3 April 2009

An Older Look at PSA Screening

A previous wiki succinctly discussed the two recent large studies—77,000 in the U.S. and 182,000 in Europe—regarding prostate cancer and the efficacy of PSA screening. Nevertheless, some history might be useful. Back in the late 1990s a major issue was the treatment effectiveness of radioactive seed implantation, SI, as compared to the supposed “gold standard” of radical prostatectomy, RP. Because prostate cancer is slow growing, urologists insisted that seven years since the inception of SI treatments was not enough data because more time was needed to properly compare the two treatments. This issue has largely been resolved in the ensuing decade to the point where urologists no longer invoke the phrase gold standard and now offer either SI or RP to their patients.

The PSA test was originally conceived as a monitoring method to judge the condition of those who were already diagnosed with prostate cancer, as opposed to acting as a screening test to determine if prostate cancer was present. Like many blood tests, it is merely an indicator; for the PSA test particularly, the result can vary according to the size of the gland, presence of infection or inflammation, how recently an ejaculation occurred, and, of course, whether cancer is present. Men started to demand the PSA and an expensive industry took off precisely because of the plausible, but ultimately empirically unwarranted belief that prompt intervention promoted the saving of lives.

However, even back then it was suspected that whatever the treatment,—SI, RP, cryotherapy, watchful waiting, electron beam radiation—the mortality rate was more or less the same. Said another way, (mass) “screening” as opposed to “testing” was of doubtful value because if the prostate cancer was indolent the patient would die with it rather than of it, and if the prostate cancer was aggressive, none of the treatments would do much good.

Discussion

1. One often hears the term, “five-year survival rate.” Some researchers consider this term completely misleading especially when applied to prostate cancer treatments. What is misleading about it? Why is mortality rate a better way of comparing treatments?

2. Consider the following statement: “The U.S. Preventive Services Task Force (USPSTF) concludes that the evidence is insufficient to recommend for or against screening asymptomatic persons for lung cancer with either low dose computerized tomography (LDCT), chest x-ray (CXR), sputum cytology, or a combination of these tests.” Go to here for the rational. How does this accord with screening for prostate cancer?

3. Find a friendly librarian to determine the percentage of watchful waiting treatment of prostate cancer in western European countries compared to the U.S. Do likewise for RP and SI. Assuming that RP is the most aggressive and watchful waiting the least aggressive, where does the United States stand?