Slashdot Mirror
65% of Cancers Caused by Bad Luck, Not Genetics or Environment
BarbaraHudson writes The Wall Street Journal and the CBC are reporting that about two-thirds of cancers are caused by random chance. From the WSJ: "The researchers, from the Johns Hopkins University School of Medicine in Baltimore, analyzed published scientific papers to identify the number of stem cells, and the rate of stem-cell division, among 31 tissue types, though not for breast and prostate tissue, which they excluded from the analysis. Then they compared the total number of lifetime stem-cell divisions in each tissue against a person's lifetime risk of developing cancer in that tissue in the U.S." The correlation between these parameters suggests that two-thirds of the difference in cancer risk among various tissue types can be blamed on random, or 'stochastic,' mutations in DNA occurring during stem-cell division, and only one-third on hereditary or environmental factors like smoking, the researchers conclude. 'Thus, the stochastic effects of DNA replication appear to be the major contributor to cancer in humans.'" The CBC reports: "The researchers said on Thursday random DNA mutations accumulating in various parts of the body during ordinary cell division are the prime culprits behind many cancer types. They looked at 31 cancer types and found that 22 of them, including leukemia and pancreatic, bone, testicular, ovarian and brain cancer, could be explained largely by these random mutations — essentially biological bad luck. The other nine types, including colorectal cancer, skin cancer known as basal cell carcinoma and smoking-related lung cancer, were more heavily influenced by heredity and environmental factors like risky behavior or exposure to carcinogens. Overall, they attributed 65 percent of cancer incidence to random mutations in genes that can drive cancer growth."
The headline is shocking when one consider the steep rise of cancer since 1945. If it was luck, then how it could change over time?
But I think the paper could still be a valuable contribution, it is just that this summary ignores the difference between cancer initiation and cancer promotion. Many environmental factors favor existing tumors but do not create them. Hence initiation can be random, while promotion can be environment-induced.
Leave out the top two, by far the most common, and the remaining top two are still predominantly hereditary and or environmental.
From: http://apps.nccd.cdc.gov/uscs/toptencancers.aspx
Top 10 Cancer Sites: 2011, Male and Female, United States Rates per 100,000
1. Prostate 128.3
2. Female Breast 122.0
3. Lung and Bronchus 61.0
4. Colon and Rectum 39.9
then a big drop in numbers before you see ...
5. Corpus and Uterus, NOS 25.4
Me thinks somebody is playing funny buggers with the numbers to get some funding for their particular line of research, while undermining the preventative medicine message at the same time. Evil.
There's a big difference between saying "most cancers are caused by random chance" and saying "there aren't specific substances that cause cancer."
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
That's all pretty muddy thinking. Suppose that all cancers are decided by a roll of a set of dice, and carcinogens and genetics merely control how many black and green faces there are on the dice. Then a cancer is never just a matter of luck or carcinogens but always both. But it's still possible to conclude that there would be 35% less cancers if we kept the carcinogens down. Or put differently, we shouldn't hope to be able to cut in half the number of cancers by just removing carcinogens, because it just doesn't have enough impact. So you have a potentially very valuable research result, but it gets interpreted in a nonsensical manner.