Why Most of What You've Heard About Cancer Is Wrong
Science author George Johnson says we need to rethink our understanding of this most devastating of diseases—and when you read some of the surprising cancer facts in his latest book, you'll see why.
Cancer. In medicine, there's no word more dreaded, more terrifying. Sure, we try to put a hopeful spin on it, celebrating cancer survivors for their bravery and their determination in fighting back. But for most of us cancer remains synonymous with death, pain, and suffering. At least, we hope, until somebody finds a "cure."
But modern science suggests we've been thinking about this dreaded disease all wrong. Yes, cancer is terrible, but paradoxically, the mechanisms behind it are at the heart of what it means to be alive in the first place. Cancer isn't a bug, unfortunately; it's looking more and more like a feature. If we haven't beaten it yet, that may be why.
This week on the Inquiring Minds podcast, we speak with veteran science journalist George Johnson, whose new book, The Cancer Chronicles: Unlocking Medicine's Deepest Mystery, helps turn much traditional thinking about cancer on its head. It's a provocative and also a personal exploration of the myths and misunderstandings that surround this most formidable enemy to our health and well being:
In the book, Johnson cites a stunning estimate by MIT cancer researcher Robert Weinberg: About 4 million of our body's cells are dividing and copying their DNA every second of every day. With every replication, there is a potential for mistakes, and a risk of developing cancer. Thankfully, we've evolved solutions to rogue errors, and our bodies can repair or destroy precancerous cells the vast majority of the time. Yet the risk can never be zero, because without this process of cell division and regeneration, we would quickly cease to live.
In fact, without the capacity for cellular mutation and the ability to pass on reformatted DNA to our offspring, our species would not have been capable of evolving. We wouldn't be who we are today. "There's something unfortunately natural about cancer," explains Johnson. "It's a natural tradeoff of evolution."
Another scientist cited by Johnson, Princeton's Robert Austin, has even suggested that cancer is a natural by-product of the body's response to stress. When faced with a scarcity of resources, bacteria respond by creating offspring and encouraging mutations, one of which just might lead to a better chance of survival. Descendants of bacteria, the cells in our own bodies have maintained this survival instinct, and also have the propensity to wiggle out of sticky situations by mutating, even if it poses a deadly risk to the larger organism of which they're part.
Cancer, in other words, isn't about destroying; it's about surviving.
Here are nine insights from Johnson's book and his Inquiring Minds interview that may dramatically change your views about cancer:
1. Lots of other animals get cancer, though not as often as us. According to Johnson, "mammals appear to get more cancer than reptiles or fish, which in turn get more cancer than amphibians. Domesticated animals seem to get more cancer than their cousins in the wild. And people get the most cancer of all." Why? It's likely a function of age. Cancer seems to come in two types: childhood cancers, which are comparatively rare, and—much more commonly—cancer that results from the gradual accumulation of mutations over the years.
"There's more cancer today because there are more people today, and 75 percent of cancer is diagnosed in people 55 years or older," says Johnson. Since cancer results largely from cell replication errors, the older you are, the more often your cells have divided and thus the greater your risk of developing cancer. The same is true for other species, which is why domesticated animals seem to get more cancer than their short-lived peers in the wild. Fish, reptiles, and amphibians also tend to have shorter lifespans than mammals, and as our ability to fight off infectious diseases and other early killers has extended our own lifespans, we're now living long enough to die from cancer instead.
2. When we say "other animals," that includes dinosaurs. Fascinatingly, Johnson starts out his book with, of all things, a case of dinosaur cancer. Or at least, a tumor found in the fossilized bone of a dinosaur. Johnson relates the story at more length here, but here are the basics: After an intriguing dinosaur fossil was found in a rock shop in Colorado, it was analyzed and a scientific paper was published in the journal The Lancet suggesting that the dinosaur had suffered from metastatic bone cancer. From Johnson's perspective on cancer, this makes total sense: Dinosaurs were very large animals that had lots and lots of dividing cells. So we'd expect that at least some of them would have developed cancer.
3. Eating fruits and vegetables is *not* proven to reduce your cancer risk. Despite the myriad health benefits of eating well, Johnson explains that large-scale studies have failed to show a strong relationship between consuming more fruits and vegetables and a lower incidence of cancer. "That was a huge surprise," says Johnson. But as he explains, while older studies had suggested benefits from this diet, more recent epidemiological studies have cast doubt on this relationship.
Often, we're told that nutrients in superfoods like spinach, carrots, and mangoes can help our bodies fight cancer. The idea is that anti-oxidants in such foods fight free radicals, atoms or groups of atoms with an odd number of electrons in their outer shells that can cause damage when they interact with a cell's DNA or its outer wall. Antioxidants like vitamins E and C and beta-carotene counteract and neutralize free radicals, and so the theory is that we can prevent damage to our DNA by consuming larger quantities of them. But clinical trials using vitamin supplements have actually shown increased risk of cancer in certain populations, and have cast doubt on the significance of micronutrients in reducing your overall mortality.
But when it comes to diet, consuming too many calories and becoming obese does increase your cancer risk. Whether sugar itself fuels cancer activity more than it does activity in other cells remains up for debate. There is a solid link, however, between cancer and chronic inflammation, the body's natural defense against all manner of cellular injuries. And excess consumption of sugar, in addition to eating trans fats and refined carbs, can cause chronic inflammation.
4. Taller people have a bigger cancer risk. Surprisingly, one major cancer risk is your height. In fact, Johnson notes, one large study found that "every four inches over 5 feet increased cancer risk by 16 percent." The likely reason: If you're tall, you have more cells in your body, and thus more opportunities to get cancer when cell division goes awry. "People who are taller had more cellular divisions to produce the taller body and therefore more chance to accumulate these mutations along the way," says Johnson. "This is not something you can do anything about."
Additional intriguing evidence of the height-cancer relationship comes from a group of Ecuadoran villagers who suffer from Laron syndrome, a type of dwarfism. Johnson reports that "because of a mutation involving their growth hormone receptors, the tallest men are four and a half feet and the women are six inches shorter…They hardly ever get cancer or diabetes, even though they are often obese."
5. With each menstrual period, a woman increases her breast cancer risk. Another surprising finding is that delaying childbearing and having fewer children might be leading to more cancers in women. "With each period a jolt of estrogen causes cells in the uterus and mammary glands to begin multiplying, duplicating their DNA—preparing for the bearing and the nursing of a child that may not come," Johnson writes. "Each menstrual cycle is a roll of the dice, an opportunity for copying errors that might result in a neoplasm. Estrogen (along with asbestos, benzene, gamma rays, and mustard gas) is on the list of known human carcinogens published by the federal government’s National Toxicology Program." Today, women are getting their periods earlier, having fewer children, and having them later, increasing the total number of estrogen surges that they experience over their childbearing years. Breast-feeding reduces estrogen, so even lactation has a somewhat protective effect.
We can't yet quantify the risk, but "delayed childbearing has been linked to an increased number of breast cancers, and it's believed to be one of the reasons why there is more breast cancer in the developed world than in developing countries where women don't have that choice and must be pregnant all the time," says Johnson.
6. Radiation in specific frequencies (UV, gamma, X-rays) can cause cancer, but not all radiation is created equal. Radiation from microwaves, cellphones, and radios is low frequency, and does not have enough energy to mutate DNA and cause cancer, according to the America Cancer Society. Most of the radiation that is cancer-causing on Earth comes from cosmic background radiation and radioactive elements found naturally in the soil. It's not man-made.
7. If you get cancer, your job may not ultimately be protected. Johnson's book ends with a story of his brother Joe, who, having exhausted his sick leave during his cancer treatment, was let go from his job. With apologies, of course.
Can your employer actually do that? Turns out it's very complicated. Stories of firings over cancer are rampant on the internet, and it's pretty clear that some cases are indeed discriminatory. Under the Americans With Disabilities Act, employers are required to make "reasonable accommodations" for those who are disabled, which can include cancer victims. That means that if you have cancer, your employer may need to take a variety of steps to allow you to continue to do your job—but the accommodations are not absolutely unlimited. The line is drawn where such accommodations become an "undue hardship (i.e., a significant difficulty or expense)" to employers, and if you can no longer perform your job's "essential functions."
Which is not to say it's fair. For many cancer patients, returning to work is a significant part of rebuilding a life after cancer, and losing a job can be a major psychological setback. Arguably, the resulting depression can sap physical resources and immunity, eventually making the recurrence of cancer more likely.
8. Cancer learns. When cancer metastasizes in your body, it's not just that a tumor gets bigger or spreads around. It mutates and evolves, learning to tap into your circulatory or other systems and to use your body for its own purposes.
"More and more, [cancer cells] are thought of as quasi-creatures that are trying to evolve in your body," says Johnson. "Because really what a cancer cell is doing in your body is…what a creature in an ecosystem is doing. It's giving birth to offspring, its cells are dividing and making daughter cells, and along the way, there are mutations—some of these mutations are beneficial to the cancer cell…They become fitter and fitter in the ecosystem of your body, but ultimately they kill the host."
9. The idea of a "cure" for cancer may be a misnomer. After decades of research, scientists are faced with the fact that most cancers result from the very cellular activities that support life, not exclusively from destructive environmental factors like cigarette smoke and UV rays. And if that's the case, then fixing the mechanisms that make cancer possible would also disrupt cellular functions that keep us alive and evolving.
So what does that say about "curing" cancer? Cancers in children tend to include fewer mutations, making them more curable, but in older patients, whose cancers result from the accumulation of many mutations over time, it's a different story. "The best response might not be to fight back with chemotherapy and radiation, increasing the stress," writes Johnson, "but to somehow maintain the exuberant cells—the tumor—in a quiescent state, something that can be lived with."
For the full interview with George Johnson, listen here:
This episode of Inquiring Minds, a podcast hosted by best-selling author Chris Mooney and neuroscientist and musician Indre Viskontas, also features a discussion of the science of hangovers (timed just for Halloween weekend, we know) and new findings about the origins of the SARS virus.