Why your doc needs a refresher course in statistics
How good is your doctor at math?
I know it seems like a strange question. But the answer could be more important than you might ever imagine. It turns out that your doctor's less than stellar math skills are likely to lead you to be subjected to unnecessary...and potentially harmful...cancer tests.
Now as a regular reader you're already well aware of the growing twin epidemic of over-screening and over-diagnosis in this country. For example, I've written to you before about the travesty that is the annual PSA test.
Men are led to believe that these yearly tests are all that stand between them and prostate cancer. But PSA tests often lead to unnecessary biopsies of slow-growing tumors that may leave you with permanent sexual dysfunction or in diapers. And the truth is lots of men get cancer and never have a high PSA reading and lots of other men have elevated PSA's and never get cancer.
Then there's the annual mammogram, which is, at best, unreliable and at worst may be responsible for inducing cancer in some women. Besides the extra shot of radiation that women are being subjected to every year the test can lead to further, even more invasive tests and side-effect laden treatments that, in the end, may not be of any benefit.
So why then do so many doctors enthusiastically push these and other dubious tests on their patients? According to the results of a recent survey published in the journal Annals of Internal Medicine it may all simply boil down to your doctor's inability to grasp statistics.
Survival rate numbers may mislead docs
Three fourths...or 76 percent...of the over 400 doctors surveyed in the poll believe that better survival rates prove that cancer screening is a lifesaver, when this is in fact not the case. And almost half of the doctors...49 percent...firmly believe that early detection is the key to saving lives, when statistics show that this simply is not true.
You see, the problem is that if you're just looking at the surface numbers can lie. For example, screenings automatically increase survival rates. That's a fact. And, unfortunately, many doctors walk away at this point armed only with that fact.
But according to a Reuter's interview with Dr. Otis Brawley, chief medical officer of the American Cancer Society, when you dig a little deeper, and have a better understanding of statistics, the picture becomes much clearer.
Dr. Brawley points out that this rise is simply because the very act of finding a tumor means people are living longer with their cancer diagnosis than if they had waited for symptoms to appear before seeing a doctor. And this automatic bump in survival rate is, of course, regardless of whether anything is ever done to treat them or not.
Irrelevant data...real world consequences
The fact is your doc's misunderstanding of statistics...or his inability to decipher the meanings behind them...can add up to real-world consequences for you.
When researchers asked doctors if they would recommend a test that increased the 5-year survival rate from 68 percent to 99 percent, 62 percent enthusiastically responded that they would definitely recommend the test with 82 percent saying that the test "saves lives from cancer."
In fact, they were three times more likely to recommend that test than one the researchers described as cutting the death rate from 2 in 1,000 people to 1.6 in 1,000. Only 23 percent of the doctors said they would recommend that second test and 60 percent felt that such a test would "save lives from cancer."
What the doctors who were more likely to recommend the test in the first scenario failed to realize is that the survival rate statistic is essentially irrelevant data...it can't be used to prove that a screening reduced cancer deaths. However, the death rate change described in the second scenario is much more relevant, and is really the only statistic that can be used to prove that a test saves lives.
The bottom line is that there's a very good chance that your doctor at some point will order an unnecessary test for you. Your best defense is to ask questions about the potential harms and benefits of any test that is recommended for you.
According to Dr. Brawley if you hear your doc utter the words "increased five year survival" during that conversation a red light should go off because, "...that's an indication that their doctor doesn't know what they are talking about."
Which reminds me of an old saying that's sometimes attributed to Stalin that goes "When one man dies it is a tragedy, when thousands die it's statistics."
And, well, it would appear that we...like those thousands...might simply just be the victims of higher math.
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About the author
Nationally acclaimed as America’s “Nutrition Physician,” Dr. Spreen has been helping people stay healthy and disease-free as a private doctor, published author, and noted researcher.
In addition to his role as a Senior Member of the prestigious Health Sciences Institute Advisory Panel in Baltimore, MD, Dr. Spreen also coaches diving at the international and Olympic levels. NorthStar Nutritionals is proud to have Dr. Spreen as our Chief Research Advisor.
Dr. Spreen also writes the Guide to Good Health.