Well … This isn’t going to make too many prostate cancer survivors happy (or too many urologists either). And it may even affect where they all go to get reliable information on their next television or washer/dryer combo!
Yesterday the well known Consumer Reports (a publication of the Consumers Union, a “public watchdog” organization) published an article entitled “Overselling cancer tests” on the value of a number of different cancer screening tests. The use of an annual PSA screening test for risk of prostate cancer didn’t make the cut!
You have to be a subscriber to Consumer Reports to read the full report. However, you can get the gist of their view of the available data from any number of other online news reports issued late yesterday or early today. Here is a brief list of some of the links:
- “Consumer reports tackles cancer screening tests” on the ABC News web site
- “Consumer Reports’ cancer screening ratings offer surprising results” on the MSN web site
- “Which cancer screenings should you skip? Consumer Reports weighs in” on Boston.com (the web site of The Boston Globe)
Of course the other way to look at this is to say to oneself that if you have been trusting Consumer Reports regarding things like cars, dishwashers, and laptop computers for the past 10 or 20 years, you may want to listen to them now too. They are not saying that the PSA test is useless. They are saying that it has to be used thoughtfully and carefully.
Filed under: Diagnosis, Risk Tagged: | PSA, risk, screening, test
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How much can one trust CU? I quit our subscription 35 years ago when I noticed how they had a decided bias against American-made hard goods, especially cars. I worked in the auto industry and was appalled at how they over-rated the foreign iron. CU has biases that one has to be aware of.
Is it better to be diagnosed because of PSA testing when you have one positive core and a negative DRE, or not have PSA testing and wait until the DRE is positive and you have capsular extension or lymph node invasion?
The Consumer Reports article bring up some valid issues to consider with respect to prostate cancer screening. Unfortunately, they once again repeat the U.S. Preventive Services Task Force’s erroneous statistics for the relative benefits and harms of prostate cancer screening.
They restate the USPSTF conclusion that for every 1,000 men screened, at most one life is saved, whereas 40 extra men will suffer impotence or incontinence. Unfortunately, this is comparing apples and oranges. Specifically, it is comparing the screening group with two completely different control groups.
The 40 extra men is comparing a screening group with a control group that is never diagnosed or treated for prostate cancer. So, they assume that in 1,000 men screened, 110 will be diagnosed, 100 will be treated, and 40 will have impotence or incontinence. The implicit control group has zero men diagnosed or treated. This is an unreal control group — in the real world, there will be prostate cancer diagnosis and treatment even without PSA screening, albeit on average at a later stage of prostate cancer.
In contrast, the one extra life saved is from the European study. It compares the prostate cancer deaths in the screening group to the prostate cancer deaths in the control group, which did also have considerable prostate cancer diagnoses and treatment. Presumably if no one in the control group was allowed to be treated for prostate cancer, there would be more of a life-saving differential.
The European study also suggests that prostate cancer screening results in about 74 out of 1,000 men receiving some treatment other than watchful waiting, compared to 51 out of 1000 men receiving such treatment in the control group. The difference between the two groups is 23 extra men out of 1000 receiving some treatment other than watchful waiting for prostate cancer.
If one assumes that 40% of those 23 extra men would have impotence or incontinence, then prostate cancer screening would lead to an extra nine out of 1,000 men having those serious side effects. The ratio of serious side effects to lives saved is 9 to 1, not 40 to 1. I think this makes some difference to how to think about the screening issue.
It also makes some difference to how to think about the treatment issue. The statistics imply a 40% risk of serious side effects from treatment. The one life saved per 23 extra men treated implies that the treatment reduces the risk of dying from prostate cancer after 11 years by between 4 or 5%. In contrast, if we needed to treat 100 men to save 1 life, as the USPSTF implies, then the treatment reduces the risk of prostate cancer death by only 1%. A 1% vs. 40% comparison of relative risks is quite different from a 4 to 5% versus 40% comparison.
I wrote Consumer Reports a letter raising some of these issues about their uncritical use of the USPSTF statistics. They acknowledged my letter. It will be interesting to see if they have any substantive response.
I do not agree with the webmaster’s conclusion, “They are not saying that the PSA test is useless. They are saying that it has to be used thoughtfully and carefully.” I did not read this in their article whatsoever. They ranked the PSA as “very unlikely the benefits outweigh the harm” and they put it in the group “Avoid These Screenings.” I believe their article is more harmful than you do. You appear to sugar-coat their bitter pill, Regards, George
Dear George:
You are — of course — entirely entitled to your opinion. However, I think you are missing a key part of the point of my comment, which relates to the term “screening”.
Frankly, as an annual screening methodology suitable for all men over (say) 50 years of age, The “New” Prostate Cancer InfoLink is in complete agreement with Consumer Reports (and others): this is not an appropriate application of the PSA test. Why? Because it begins by making the utterly inappropriate assumptions that: (a) the PSA test is in some way specific for prostate cancer (which it isn’t) and (b) all men are at roughly comparable risk for prostate cancer (which they aren’t).
We have discussed this issue frequently and extensively over the years. There are definable subsets of men for whom annual PSA testing is very probably a very good idea because they are at high risk for clinically significant prostate cancer for a variety of reasons. There are a whole bunch of other men who are at relatively low risk for clinically significant prostate cancer and in whom annual PSA tests are a near to guaranteed method of finding low-risk prostate cancer that never needs to be treated. Such men are likely much better off if they get a baseline PSA test at some point and then follow-up tests at (say) 5-yearly intervals (unless the need for a test is suggested by other factors).
It also needs to be much more widely recognized that a single PSA level taken at a particular point in time can be affected by a vast variety of things that have nothing to do with prostate cancer at all, and so a mildly elevated PSA result should probably lead to a repeat PSA test within a month or so as opposed to an immediate rush to biopsy.
The Consumer Reports material focused exclusively on the utility of the PSA test as a means of “screening” all men annually for their risk for prostate cancer. It is only in that context that the magazine is suggesting that “the benefits largely outweigh the harms”. The “New” Prostate Cancer InfoLink has never endorsed the annual use of PSA tests to screen for prostate cancer except in those men who have clear risk factors for prostate cancer based on their family history, ethnicity, a PSA at baseline of > 1.0 ng/ml in their 40s, or certain other risk factors (e.g., specific types of employment like working in cadmium mining or refining facilities).
The PSA test has some very valuable characteristics and uses. … It’s application to screen most men on an annual basis for their risk of prostate cancer is not one of those valuable characteristics and uses. One of the values of the PSA test is to assess the potential for risk of prostate cancer in appropriately selected individuals … but that is not the same as mass population screening.