Is cancer just bad luck? Lifestyle factors a lesser risk than previously thought, study shows

A study looked at 32 cancers and risk factors including environment, lifestyle, heredity and random DNA copying errors. The latter were responsible for two-thirds of genetic changes that lead to the disease, but there were big variations

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Published: 7:02am, 12 Jun 2017Updated: 4:20pm, 12 Jun 2017

We’ve all heard of one person who stuck to a healthy diet all their life, exercised regularly, never smoked or overindulged in alcohol, and yet, despite following all the “rules”, ended up being diagnosed with cancer. That’s just bad luck, some may say, and, according to new research from Johns Hopkins University in the US, such a call may not be that far-fetched.

Authors of the study: Cristian Tomasetti (left), assistant professor of biostatistics at the Johns Hopkins Kimmel Cancer Centre; and Bert Vogelstein, co-director of the Ludwig Centre at the Johns Hopkins Kimmel Cancer Centre.

The study, authored by Bert Vogelstein and Cristian Tomasetti at the Johns Hopkins Kimmel Cancer Centre, found that many cancers are not only unavoidable, but actually have less to do with environmental, lifestyle or hereditary factors and more to do with random DNA copying errors or typos. In other words, cancer is partly caused by bad luck.

Cancer is a disease involving the genes of cells. According to Dr Au Siu-kie, a specialist in oncology at Hong Kong Adventist Hospital these cells have acquired the ability of uncontrolled growth, evading the body’s normal control mechanism and immune surveillance. These extra cells may form a mass of tissue, called a tumour, infiltrating and destroying neighbouring organs, or spreading through the blood or lymphatic vessels to other organs.

“Unlike normal cells, the genetic make-up, or genome, of cancer cells is highly unstable, and further genetic changes accumulate as the cells divide, generating multiple clones of cancer cells with different genetic alterations,” says Au.

In the study, published in March this year in the journal Science, Vogelstein and Tomasetti looked at 32 types of cancer and noted that, overall, about 66 per cent of genetic mutations that lead to the disease were the result of random DNA copying errors; 29 per cent were due to environmental and lifestyle factors; and the remaining five per cent were inherited.

Banded DNA sequences. Many cancers are caused by errors that occur when copying DNA. Photo: Shutterstock

Looking at the different cancers, the researchers found that some were more likely the result of environmental factors, while other cancers were due more to random mutations than to environmental or hereditary factors. For instance, they found that 65 per cent of the mutations that cause lung cancer are due to lifestyle or environmental factors like smoking, while only 35 per cent are from random DNA copying errors.