The real way to prevent cancer

Long, long ago, seemingly in a galaxy far, far away, I first encountered quackery on the Internet. Because I am a cancer surgeon, naturally I gravitated towards cancer quackery at first. Believe it or not, it was quite some time after that before I started to take an interest in what has become a major focus of this blog, the antivaccine movement and the misinformation it spreads. Both are equally damaging in their own way. True, these were back in the deep, dark days when I used to cruise various Usenet newsgroups, ranging from alt.revisionism (Holocaust denial), sci.skeptic (of course!), and, where I cut my teeth looking at pesudoscientific and antiscientific health claims. By the time I started blogging I had become all too acquainted with antivaccine wingnuttery.

Even way back then, if there was one thing I learned about aficionados of alt-med, it’s that they have a near mystical belief in the power of diet and other lifestyle interventionsn to cure all ills. In fact, when it comes to cancer, it’s not uncommon to find claims that it is possible to prevent almost all cancer. Typically, the argument in essence boils down to denialism of genetics. In other words, some of the more radical proponents claiming that we can virtually totally control whether we get cancer or not will gloat about how the “genetic trail hasn’t led to a cure” and that genetics accounts for far fewer cancers than previously thought. They will seize on studies from the relatively new field of epigenetics as evidence that nearly all cancer is caused by environmental influences. The statement is, of course, that we can control our health. The implication underlying that statement and assumption is that if someone is not healthy it is his fault. As I’ve said, it’s the Law of Attraction, in which intent is all; i.e., wishing makes it so. Often reasonable cancer-preventing strategies based in science are heavily leavened with woo and quackery.

The magical thinking of many alt-med mavens aside, however, it is true that a significant number of cancers could be prevented by lifestyle modifications. Conventional medicine recognizes this and has long recognized this. The number is not insubstantial, either. Again, conventional medicine has recognized this. However, realizing the power of prevention of cancer does not require a raw vegan diet, a boatload of supplements, or invoking magical mystical universal energies. Conventional medicine tells us that it takes a few simple things, and the incidence of cancer could be cut by as much as 50%. Indeed, a report on the Union for International Cancer Control (UICC) World Cancer Congress 2012 tells us so:

More than 50% of cancer could be prevented if people simply implemented what is already known about cancer prevention, according to a researcher here at the Union for International Cancer Control (UICC) World Cancer Congress 2012.

Graham Colditz, PD, DrPH, from the Washington University School of Medicine in St. Louis, Missouri, reported that a number of interventions, largely involving lifestyle behaviors, but also involving higher-cost interventions in high-income countries, could prevent a large proportion of cancers in 15 to 20 years if widely applied.

So what is already known about cancer prevention? The “biggest buy” would come from a simple intervention that virtually all of us know about. That’s not to say it would be easy. Far from it. But it is simple: Get more people to stop smoking. One-third of cancer cases in developed countries can be attributed to smoking. It’s just that bad. Colditz points out that it is possible to reduce smoking-related cancers dramatically:

“One third of cancer in high-income countries is caused by smoking,” Dr. Colditz said. If smoking rates could be reduced to the current levels in Utah [about 11%], the United States could see a 75% reduction in smoking-related cancers in 10 to 20 years — a target that Dr. Colditz feels is feasible in countries where smoking rates have already declined considerably.

Unfortunately, the number of people in the rest of the US who smoke is nearly twice that percentage; so this is not an easy task. Tobacco control efforts have floundered upon the rocks of human nature time and time again. It’s one of those things that easy to say but oh-so-hard to do.

Here’s another thing that’s equally hard to do:

Similarly, it is estimated that being overweight or obese causes approximately 20% of cancer today. If people could maintain a healthy body mass index (BMI), the incidence of cancer could be reduced by approximately 50% in 2 to 20 years. (A healthy BMI for cancer prevention is from 21 to 23 kg/m², as other speakers pointed out.)

Which is, of course, related to this:

Dr. Colditz, among others, estimates that poor diet and lack of exercise are each associated with about 5% of all cancers. Improvement in diet could reduce cancer incidence by 50% and increases in physical activity could reduce cancer incidence by as much as 85% in 5 to 20 years.

I must admit that I was a bit confused by this paragraph. If poor diet and lack of exercise are assocaited with about 5% of all cancers, how could improvement in diet reduce cancer incidence by 50% and increases in physical activity could reduce cancer incidence by 85%? I assume that what is meant is that improvements in diet would reduce cancer incidence by 50% within those 5% of cancers associated with diet and that increased physical exercise could decrease cancer incidence by 85% within the 5% of cancers associated with a sedentary lifestyle. Otherwise, all the percentages start adding up to more than 100%. Be that as it may, it should be noted that, contrary to the rants of alt-med enthusiasts, science-based medicine doesn’t deny that alterations in diet and lifestyle can reduce the incidence of cancer. What alt-med enthusiasts don’t like is that the data don’t support their claims; the true effect of these interventions on cancer is not as potent as they believe (and would have you believe). That’s not at all to say it’s not worth it to correct these problems. After all, obesity, poor diet, and sedentary lifestyles are associated with more than just cancer. They’re associated with cardiovascular disease and type II diabetes as well.

Under science-based medicine, there are many reasons to do these things, both at the population and individual level. At the population level, doing these things would definitely impact the incidence of cancer. At the individual level, doing these things make people healthier and less prone to a wide variety of diseases.

Of course, what amuses me most about this article is the rest of the science-based interventions that would decrease the incidence of cancer. I’ll give you a hint.

Just a little hint.

Keep scrolling down a little more.

It’s really going to shock you.

It involves…vaccines! Yes, vaccines:

Eradicating the main viruses associated with cancer worldwide by implementing widespread infant and childhood immunization programs targeting 3 viruses — human papillomavirus and hepatitis B and C — could lead to a 100% reduction in viral-related cancer incidence in 20 to 40 years, he added.

And the dreaded pharmaceuticals:

Then there are the “higher tech” interventions that, at least in high-income countries, could prevent a significant proportion of cancer and cancer-related mortality, starting with breast cancer.

“We have shown that tamoxifen reduces the rate of both invasive and noninvasive breast cancer by 50% or more, compared with placebo, at 5 years,” Dr. Colditz said.

And more pharmaceuticals and—gasp!—screening:

In addition, Dr. Colditz noted that approximately 20 years of follow-up has shown that aspirin is associated with a 40% reduction in mortality from colon cancer. Screening for colorectal cancer has a similar magnitude of mortality reduction (30% to 40%).

So what is the real way, as opposed to the fantasy way, to prevent cancer? It’s simple (although not easy). Don’t smoke. Lose weight. Exercise. Eat a healthy diet (and, no, that diet doesn’t have to be a raw vegan diet, as some would have you believe). Get your vaccines. Get screened for certain diseases. If you’re at a high risk for cancer, use science-based regimens that might involve taking, yes, pharmaceutical products to reduce your risk.

Because, in the end, cancer is complicated. It’s not a single disease. In fact, individual cancers can be argued not to be single diseases in that they exhibit incredible heterogeneity within individual tumors. So is preventing cancer.