Thank you Gary Schwitzer for addressing absolute versus relative risk, despite the media’s (and some researchers’) viewing the Tamoxifen issue as proof of patients’ stupidity.
I’m going to start with the conclusion of the New York Times column that inspired this commentary, in which a doctor at Memorial Sloane-Kettering dismisses the Tamoxifen problem as something that will be solved by aromatase inhibitors, the new generation of anti-estrogen therapy. I have news for the oncology community: aromatase inhibitors won’t change a thing.
Women don’t take these pills, and doctors don’t understand why, because they each hold a very different view of their costs and benefits. I used the term costs rather than risks for a reason, because this has very little to do with women over-rating the rare fatal side effects (those are a factor, but they’re not the factor). To explain, let me start with a simple cost-benefit matrix since, unlike a risk tolerance matrix, it puts a different emphasis on probability:
A typical risk tolerance grid, which is what seems to drive oncology research, says, in a nutshell, that the bigger the harm, the more risk averse we become, and the more we’ll do to avoid it (the upper right hand corner in that kind of matrix is usually an angry red). But in a cost-benefit matrix, this quadrant merely represents big gains in exchange for big costs. If the gains minus the costs are a wash, most people would rationally be neutral; so, the difference between the gain and the cost, or the probability of achieving the gain (or incurring the cost) become crucial.
When researchers broadcast juicy numbers about population risk and a risk-reducing drug, they’re almost always describing the bottom right-hand corner (huge benefit, small sacrifice), and almost as frequently understating the full costs as well as overstating the benefits. This New York Times column is a typical example. I can forgive anyone who read that column and came away thinking that taking Tamoxifen is a no-brainer and that patients are fuzzy headed at best.
Remember Henery Hawk, that little chicken hawk who was always pestering Foghorn Leghorn? That’s the image that should come to mind the next time you read of a little 12-person (or 20-rat, or 40-mouse) study claiming to have found a cure for cancer, wrinkles, or even boredom. It’s not that small studies are worthless (they’re not), it’s that they’re worthless for making Big Decisions about treatment, lifestyle, risk, or where to spend your money. The reason for this, in layman’s terms, is chance.
Soy : miracle food or devil’s spawn?
Judging from media reports, soy is a regular Dr. Jekyll-and-Mr. Hyde of foods: on the one hand,
it’s widely praised as a heart- and environment-healthy alternative to meat, and a source of important micronutrients like folate (particularly important for nursing mothers). On the other hand, it contains phytoestrogens – plant compounds that mimic, to varying degrees, the female hormone estrogen. Oncologists routinely caution breast cancer patients to consume soy in moderation or avoid it entirely. Nutritionists alternate between praising its virtues and warning against overconsumption.
Two recent studies have only added to the understandable public confusion around the safety of soy. First, a large, prospective epidemiological study in China reported that breast cancer survivors who consumed the most soy showed no greater mortality or relapse rate than those who ate the least soy. In fact, there was a statistically weak benefit for the soy lovers. On the other hand, researchers at the National Toxicology Program (NTP, a US Department of Health and Human Services program) issued a cautionary report and call for more research on the safety of soy-based baby formula, raising concerns that exposure to the concentrated soy extracts in the formulas may have detrimental effect on developing infants. Read More »