It may sound flippant to say that many cases of cancer are caused by bad luck, but that is what two scientists suggested in an article published last week in the journal Science. The bad luck comes in the form of random genetic mistakes, or mutations, that happen when healthy cells divide.
Random mutations may account for two-thirds of the risk of getting many types of cancer, leaving the usual suspects — heredity and environmental factors — to account for only one-third, say the authors, Cristian Tomasetti and Dr. Bert Vogelstein, of Johns Hopkins University School of Medicine. “We do think this is a fundamental mechanism, and this is the first time there’s been a measure of it,” said Dr. Tomasetti, an applied mathematician.
Though the researchers suspected that chance had a role, they were surprised at how big it turned out to be.
“This was definitely beyond my expectations,” Dr. Tomasetti said. “It’s about double what I would have thought.”
The finding may be good news to some people, bad news to others, he added.
Smoking greatly increases the risk of lung cancer, but for other cancers, the causes are not clear. And yet many patients wonder if they did something to bring the disease on themselves, or if they could have done something to prevent it.
“For the average cancer patient, I think this is good news,” Dr. Tomasetti said. “Knowing that over all, a lot of it is just bad luck, I think in a sense it’s comforting.”
Among people who do not have cancer, Dr. Tomasetti said he expected there to be two camps.
“There are those who would like to control every single thing happening in their lives, and for those, this may be very scary,” he said. “ ‘There is a big component of cancer I can just do nothing about.’