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Screening for disease in people without symptoms: The reality

One of the most contentious questions that come up in science-based medicine that we discuss on this blog is the issue of screening asymptomatic individuals for disease. The most common conditions screened for that we, at least, have discussed on this blog are cancers (e.g., mammography for breast cancer, prostate-specific antigen screening for prostate cancer, ultrasound screening for thyroid cancer), but screening goes beyond just cancer. In cancer, screening is a particularly-contentious issue. For example, by simply questioning whether mammography saves as many lives lost to breast cancer as advocates claim, one can find oneself coming under fire from some very powerful advocates of screening who view any questioning of mammography as an attempt to deny “life-saving” screening to women. That’s why I was very interested when I saw a blog post on The Gupta Guide that pointed me to a new systematic review by John Ioannidis and colleagues examining the value of screening as a general phenomenon, entitled “Does screening for disease save lives in asymptomatic adults? Systematic review of meta-analyses and randomized trials.”

Before I get into the study, let’s first review some of the key concepts behind screening asymptomatic individuals for disease. (If you’re familiar with these concepts, you can skip to the next section.) The act of screening for disease is based on a concept that makes intuitive sense to most people, including physicians, but might not be correct for many diseases. That concept is that early intervention is more likely to successfully prevent complications and death than later intervention. This concept is particularly strong in cancer, for obvious reasons. Compare, for example, a stage I breast cancer (less than 2 cm in diameter, no involvement of the lymph nodes under the arm, known as axillary lymph nodes) with a stage III cancer (e.g., a tumor measuring greater than 5 cm and/or having lots of axillary lymph nodes involved). Five year survival is much higher for treated stage I than for treated stage III, and, depending on the molecular characteristics, the stage I cancer might not even require chemotherapy and can be treated with breast conserving surgery (“lumpectomy” or partial mastectomy) far more frequently than the stage III cancer. So it seems intuitively true that it would be better to catch a breast cancer when it’s stage I rather than when it’s stage III.
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Posted in: Cancer, Clinical Trials, Epidemiology, Public Health

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Everything we eat causes cancer…sort of

Read meat causes cancer. No, processed meat causes cancer. OK, it’s both read meat and processed meat. Wait, genetically modified grain causes cancer (well, not really). No, aspartame causes cancer. No, this food coloring or that one causes cancer.

Clearly, everything you eat causes cancer!

That means you can avoid cancer by avoiding processed meats, red meat, GMO-associated food (no, probably not), aspartame, food colorings, or anything “unnatural.” Or so it would seem from reading the popular literature and sometimes even the scientific literature. As I like to say to my medical students, life is a sexually transmitted fatal disease that gets us all eventually, but most of us would like to delay the inevitable as long as possible and remain as healthy as possible for as long as possible. One of the most obvious ways to do accomplish these twin aims is through diet. While the parameters of what constitutes a reasonably healthy diet have been known for decades, diet still ranks high on the risk of concerns regarding actions we take on a daily basis that can increase our risk of various diseases. Since cancer is disease (or, I should say, cancers are diseases) that many, if not most, people consider to be the scariest, naturally we worry about whether certain foods or food ingredients increase our risk of cancer.

Thus was born the field of nutritional epidemiology, a prolific field with thousands of publications annually. Seemingly, each and every one of these thousands of publications gets a news story associated with it, because the media love a good “food X causes cancer” or “food Y causes heart disease” story, particularly before the holidays. As a consequence, consumers are bombarded with what I like to call the latest health risk of the week, in which, in turn, various foods, food ingredients, or environmental “toxins” are blamed and exonerated for a panoply of health problems, ranging from the minor to the big three, cardiovascular disease, diabetes, and cancer. It’s no wonder that consumers are confused, reacting either with serial alarm at each new “revelatory” study or with a shrug of the shoulders as each new alarm joins other alarms to produce a tinnitus-like background drone. Unfortunately, this cacophony of alarm also provides lots of ammunition to quacks, cranks, and crackpots to tout their many and varied diets that, they promise, will cut your risk of diseases like cancer and heart disease to near zero—but only if adhered to with monk-like determination and self-denial. (Yes, I’m talking about you, Dean Ornish, among others.)

All of this is why I really wanted to write about an article I saw popping up in the queue of articles published online ahead of print about a month ago. Somehow, other topics intervened, as did my vacation and then the holidays, and somehow I missed it last week, even though a link to the study sits in my folder named “Blog fodder.” Fortunately, it just saw print this week in its final version, giving me an excuse to make up for my oversight. It’s a study by one of our heroes (despite his occasional misstep) here on the SBM blog, John Ioannidis. It comes in the form of a study by Jonathan D. Schoenfeld and John Ioannidis in the American Journal of Clinical Nutrition entitled, brilliantly, Is everything we eat associated with cancer? A systematic cookbook review.
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Posted in: Cancer, Nutrition

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Lies, damned lies, and…science-based medicine?

I realize that in the question-and-answer session after my talk at the Lorne Trottier Public Science Symposium a week ago I suggested in response to a man named Leon Maliniak, who monopolized the first part of what was already a too-brief Q&A session by expounding on the supposed genius of Royal Rife, that I would be doing a post about the Rife Machine soon. And so I probably will; such a post is long overdue at this blog, and I’m surprised that no one’s done one after nearly three years. However, as I arrived back home in the Detroit area Tuesday evening, I was greeted by an article that, I believe, requires a timely response. (No, it wasn’t this article, although responding to it might be amusing even though it’s a rant against me based on a post that is two and a half years old.) Rather, this time around, the article is in the most recent issue of The Atlantic and on the surface appears to be yet another indictment of science-based medicine, this time in the form of a hagiography of Greek researcher John Ioannidis. The article, trumpeted by Tara Parker-Pope, comes under the heading of “Brave Thinkers” and is entitled Lies, Damned Lies, and Medical Science. It is being promoted in news stories like this, where the story is spun as indicating that medical science is so flawed that even the cell-phone cancer data can’t be trusted:

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Let me mention two things before I delve into the meat of the article. First, these days I’m not nearly as enamored of The Atlantic as I used to be. I was a long-time subscriber (at least 20 years) until last fall, when The Atlantic published an article so egregiously bad on the H1N1 vaccine that our very own Mark Crislip decided to annotate it in his own inimitable fashion. That article was so awful that I decided not to renew my subscription; it is to my shame that I didn’t find the time to write a letter to The Atlantic explaining why. Fortunately, this article isn’t as bad (it’s a mixed bag, actually, making some good points and then undermining some of them by overreaching), although it does lay on the praise for Ioannidis and the attacks on SBM a bit thick. Be that as it may, clearly The Atlantic has developed a penchant for “brave maverick doctors” and using them to cast doubt on science-based medicine. Second, I actually happen to love John Ioannidis’ work, so much so that I’ve written about it at least twice over the last three years, including The life cycle of translational research and Does popularity lead to unreliability in scientific research?, where I introduced the topic using Ioannidis’ work. Indeed, I find nothing at all threatening to me as an advocate of science-based medicine in Ioannidis’ two most famous papers, Contradicted and Initially Stronger Effects in Highly Cited Clinical Research and Why Most Published Research Findings Are False. The conclusions of these papers to me are akin to concluding that water is wet and everybody dies. It is, however, quite good that Ioannidis is there to spell out these difficulties with SBM, because he tries to keep us honest.
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Posted in: Clinical Trials, Science and Medicine

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