Cancer is often caused by the “bad luck” of random mutations that arise when cells divide, not family history or environmental causes, US researchers say.
The study, conducted by researchers at Johns Hopkins University, found a significant number of cancers were caused by pure bad luck.
While environmental factors and behaviours can add to your risk, about two-thirds of adult cancers measured could be explained by random mutation in genes encouraging tumours to grow.
The remaining one third was due to environmental factors and inherited genes.
The study is based on a statistical model that includes many types of cancer in a range of human tissues.
However it did not include breast cancer, which is the most common cancer in women, or prostate cancer, which is the second most common cancer in men after skin cancer.
“This study shows that you can add to your risk of getting cancers by smoking or other poor lifestyle factors,” said study author Bert Vogelstein, a professor of oncology at the Johns Hopkins University School of Medicine.
“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.”
He added that people who live a long time without getting cancer, despite being long-time smokers or being exposed heavily to the Sun, do not have “good genes.”
“The truth is that most of them simply had good luck,” he added.
Some 22 cancer types arising in 31 tissues studied could be traced back to random mutations, the study found.
The other nine “had incidences higher than predicted by ‘bad luck’ and were presumably due to a combination of bad luck plus environmental or inherited factors,” the university said.
These nine types included lung cancer and skin cancer – which are influenced by exposure to smoke and sunshine – as well as some cancers known to be hereditary.
The findings mean that an even greater emphasis should be placed on early detection of cancer and research that could detect these harmful random acts before they lead to widespread cancer.
— with AAP