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.”
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