Bad luck plays a major role in determining who gets cancer and who does not, according to researchers who say two-thirds of cancers of various types can be blamed on random mutations and not heredity or risky habits like smoking.
The researchers said random DNA mutations accumulating in various parts of the body during ordinary cell division were the prime culprits.
They looked at 31 cancer types and found that 22 of them, including leukaemia and pancreatic, bone, testicular, ovarian and brain cancer, could be explained largely by these random mutations – essentially biological bad luck.
The other nine types, including colorectal cancer, skin cancer known as basal cell carcinoma and smoking-related lung cancer, were more heavily influenced by heredity and environmental factors like risky behaviour or exposure to carcinogens.
Overall, they attributed 65 per cent of cancer incidence to random mutations in genes that can drive cancer growth.
“When someone gets cancer, immediately people want to know why,” said oncologist Dr Bert Vogelstein of the Johns Hopkins University School of Medicine in Baltimore.
“They like to believe there’s a reason,” he said.
“The real reason in many cases is not because you didn’t behave well or were exposed to some bad environmental influence, it’s just because that person was unlucky.
“It’s losing the lottery.”
Dr Vogelstein conducted the study published in the journal Science with Johns Hopkins biomathematician Cristian Tomasetti.
Professor Tomasetti said harmful mutations occur for “no particular reason other than randomness” when the body’s master cells, called stem cells, divide in various tissues.
He said the study shows changing one’s lifestyle and habits like smoking to avoid cancer risks could help prevent certain cancers, but may not be as effective for others.
“Thus, we should focus more research and resources on finding ways to detect such cancers at early, curable stages,” he said.
The researchers charted the cumulative number of lifetime divisions in the stem cells of a given tissue – for example, lungs or colon – and compared that to the lifetime cancer risk in that tissue.
Tissues that undergo more divisions were more prone to tumours, generally speaking.
The study did not cover all cancer types.
Breast and prostate cancer were excluded because the researchers were unable to ascertain reliable stem cell division rates.
Reuters