Researchers have found that bad luck plays a major role in determining most types of cancer, rather than genetics or risky lifestyle choices such as smoking.
The results, published in the journal Science on Thursday, found that random DNA mutations that amass in the body when stem cells divide into various tissues cause two thirds of cancers.
After examining 31 cancer types, researchers found 22 were from mutations in stem cells that could not be prevented.
Cancers that could be explained with biological bad luck included pancreatic, leukemia, bone, testicular, ovarian and brain cancer.
But the researchers say lifestyle choices such as avoiding smoking, eating healthily and staying out of the sun will help to prevent certain cancers, just not all of them.