Unhealthy diets and poor lifestyles cause three times as many cases of cancer as genetic determiners, according to an expert in the disease.
Dr Rachel Thompson, science programme manager for the World Cancer Research Fund, said people should stop thinking cancer is just down to "bad luck" or their genes.
It is believed only 5% to 10% of all cancers come from specifically inherited genes, while 39% of the most common forms of the disease – such as breast and bowel – could be prevented through a combination of a good diet, exercise and keeping weight under control.
Dr Thompson said: "It's important to dispel the myth that cancer is just down to genes. The evidence shows that an unhealthy diet and low activity levels cause three times more cancer cases than genes.
"It could possibly be even more than this. If only 5% of cancers are as a result of our genes, then an unhealthy diet and lifestyle could cause eight times more cancer cases."
She said a family history is an important source of information for some people, but overall an inherited genetic predisposition is uncommon.