Chuck Bednar for redOrbit.com Your Universe Online

Two-thirds of all adult cancer cases are primarily the result of bad luck, according to the authors of a new study appearing in Fridays edition of the journal Science.

Dr. Bert Vogelstein, the Clayton Professor of Oncology at the Johns Hopkins University School of Medicine, and Dr. Cristian Tomasetti, an assistant professor of oncology at the Johns Hopkins University School of Medicine and Bloomberg School of Public Health, developed a statistical model that measured the proportion of cancer incidence across many different tissue types.

They found that two-thirds of adult cancer incidence across tissues occur when the random mutations that take place during stem cell division drive cancer through, while the remaining one-third of cases are the result of environmental factors and inherited genes.

All cancers are caused by a combination of bad luck, the environment and heredity, and weve created a model that may help quantify how much of these three factors contribute to cancer development, explained Dr. Vogelstein, who is also co-director of the Ludwig Center at Johns Hopkins and an investigator at the Howard Hughes Medical Institute.

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, he said, adding that that poor lifestyle choices can also contribute to this so-called bad luck factor.

The authors said that the implications of their model could alter the public perception about cancer risk factors, as well as impact the funding of research related to the disease.

If most cancer cases can be explained by random DNA mutations that occur as stem cells divide, explained Dr. Tomasetti, it means that lifestyle changes will be a tremendous help when it comes to preventing some forms of the disease, but will be less effective against other types.

As a result, the medical community should should focus more resources on finding ways to detect such cancers at early, curable stages, he added. He and Vogelstein said that they reached their conclusion by searching scientific literature for data on the cumulative number of total stem cell divisions among 31 tissue types that take place during a persons lifetime.

Stem cells renew themselves, repopulating cells that die off in specific organs, the researchers said. Cancer arises when tissue-specific stem cells experience mutations in which one chemical letter in DNA is erroneously swapped for another during the replication process.

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Two-thirds of cancer cases are "bad luck," study says

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