Doctors at work at Johns Hopkins University, which conducted a new study about the role of random mutations in cancer.
Much of the war on cancer in recent years has focused on the hunt for genetic and environmental causes, but a new study says most incidences of the disease are actually the result of bad luck.
The analysis, published in the journal Science Thursday, found that random mutations that occur as stem cells divide are "the major contributors to cancer overall." Such randomness accounts for about two-thirds of cancer incidence, according to the analysis.
"All cancers are caused by a combination of bad luck, the environment and heredity, and we've created a model that may help quantify how much of these three factors contribute to cancer development," Dr. Bert Vogelstein, a professor of medicine at Johns Hopkins University school of medicine and the study's lead investigator, said in a press release. "Cancer-free longevity in people exposed to cancer-causing agents, such as tobacco, is often attributed to their 'good genes', but the truth is that most of them simply had good luck."
Dr. Louise Strong, an M.D. Anderson Cancer Center geneticist, said the paper elucidates an important concept "for a public that likes to have something to blame things on."
"This should give us pause about where to put the focus if we want to reduce cancer mortality," said Strong. "We can't expect to make a huge impact purely by addressing heritable risks and environmental factors such as smoking and radiation. We need to put more effort into developing creative, early-detection approaches."
Vogelstein's team used a statistical model that analyzed published data to identify the number of stem cells, and the rate of stem-cell division, among 31 tissue types. Comparing the total number of lifetime stem-cell divisions in each tissue against an individual's lifetime risk of developing cancer in that tissue, they found strong correlations in 22 cancer types, among them cancers that afflict the pancreas and small intestine.
In the other nine, it found a combination of randomness and risk factors could explain why the disease occurred, such as lung cancer.
The cancers studied did not include two of the most common cancers, those that afflict the breast and prostate. That brought criticism by some scientists.
The study also did not look at the factors that cause cell division, such as aging.
Dr. Sharon Plon, a Baylor College of Medicine geneticist, called the paper "an elegant way of confirming what many scientists think" but agreed with Strong that making cancer's reality understandable to a public audience carries a certain power.
"The authors' argument is that given the number of genetic mistakes that occur as cells divided, it's very hard to prevent cancer," said Plon. "It's probably more effective to develop better detection methods as early as possible.
The study is only available by subscription, but you can find the abstract here and the Johns Hopkins press release here.