Two-thirds of cancer cases caused by 'bad luck': Johns Hopkins Medicine study

Cancers due to bad luck.
Johns Hopkins University

Cancers due to bad luck.

Random luck plays a significant role in determining whether or not a person is diagnosed with cancer during their lifetime, according to a landmark study from the US.

Bad luck is responsible for two-thirds of adult cancer while the remaining cases are due to environmental risk factors and inherited genes, researchers from the Johns Hopkins Kimmel Cancer Center found.

Johns Hopkins University School of Medicine scientist Bert Vogelstein said the research explains why some people can smoke and drink into their old age while others with healthier lifestyles receive a cancer diagnosis.

Cancers due to bad luck plus environmental and inherited factors.
Johns Hopkins University

Cancers due to bad luck plus environmental and inherited factors.

"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," he said.

"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." 

The study involved comparing stem cell divisions in 31 cancer types and determining which were driven by the "bad luck" factor of random DNA mutations and which had a higher incidence due to a combination of bad luck and environmental or hereditary risk factors.

Dr Vogelstein said the findings should not be a cause for complacency.

"This study shows that you can add to your risk of getting cancers by smoking or other poor lifestyle factors," he said. "However, many forms of cancer are due largely to the bad luck of acquiring a mutation in a cancer driver gene regardless of lifestyle and heredity factors."

Co-researcher Cristian Tomasetti said the study, published in the journal Science, made a strong case for early detection. 

"If two-thirds of cancer incidence across tissues is explained by random DNA mutations that occur when stem cells divide, then changing our lifestyle and habits will be a huge help in preventing certain cancers, but this may not be as effective for a variety of others," he said.

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"We should focus more resources on finding ways to detect such cancers at early, curable stages."

The analysis did not include some cancers, including breast and prostate cancer which are two of the most common cancers in Australia, as the scientists could not find reliable data on stem cell division rates in existing research.

Director of public policy at Cancer Council Australia, Paul Grogan, said putting cancer incidence down to "luck" was an oversimplification, noting that 14,000 Australians die from cancers caused by lifestyle risk factors each year. 

"Participation in screening and surveillance programs, being vigilant about your health, getting regular check-ups, avoiding risk factors – all of these measures can help us to prevent or survive cancer, irrespective of our genes," he said.

Chief executive of the Public Health Association of Australia Michael Moore agreed luck played a role in good health but said people could still control their own fortune.

"Don't test your good luck," he said. "You can still minimise the risks by avoiding any exposure to tobacco, too much exposure to sun and obesity."

Director of programs at Cancer Council NSW Kathy Chapman said research into gene mutations would lead to improved cancer treatment.

"That would help us to understand which genes are really the important ones when somebody is diagnosed with cancer," she said. "It will help us understand at that very microscopic level which treatments will lead to the best outcomes."

 - SMH

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