healthHealth and Medicine

Two-Thirds Of Cancer Mutations Down To Random Bad Luck, Claims Study


Robin Andrews

Science & Policy Writer

Is cancer mainly determined by a genetic roll of the dice? Oleg Belov/Shutterstock

A new Science study by a team at Johns Hopkins Kimmel Cancer Center has concluded that up to 66 percent of all cancer-causing mutations are the direct consequence of entirely random DNA replication errors. Sadly, this technically makes these mutations unavoidable if we do get them.

This stark finding is based on a series of mathematical models used to predict the paths of DNA copying, along with an analysis of a pre-existing cancer data set. These mutations happen regardless of whether a person is fit or unfit, a smoker or not a smoker, and so on. General health doesn’t seem to come into it.


“We studied the relationship between the number of normal stem cell divisions and the risk of 17 cancer types in 69 countries throughout the world,” the pair of researchers write in their paper. “The data revealed a strong correlation between cancer incidence and normal stem cell divisions in all countries, regardless of their environment.”

In contrast, 29 percent of cancers are caused by environmental factors and just 5 percent appear to be hereditary.

The authors of the study are the very same behind the 2015 paper that came to a similar conclusion – that most cancers are a result of “bad luck” more than anything else. At the time, the paper attracted a lot of controversy, and this new study is likely to experience the same hostile atmosphere.

Attributing blame for cancer, according to the new study. B - brain; Bl - bladder; Br - breast; C - cervical; CR - colorectal; E - esophagus; HN - head and neck; K - kidney; Li - liver; Lk - leukemia; Lu - lung; M - melanoma; NHL - non-Hodgkin lymphoma; O - ovarian; P - pancreas; S - stomach; Th - thyroid; U - uterus. Tomasetti et al./Science


There are some things that must be underscored at this point. Cancer is hugely complicated – there are 200 types, at least, and each of them are varyingly aggressive, fatal, treatable, and curable. There are multiple ways to fight cancer, from the conventional to the cutting-edge. Some are more effective than others.

Most importantly of all, there’s a lot about cancer we are yet to understand. It’s caused by a number of environmental (radiation, carcinogens, and infections) and genetic factors, with some likely linked more closely to one rather than the other.

All this new study does is highlight that we may be underestimating the random nature of cancer-causing mutations in our DNA – and it’s not without its problems.

Although the number of cancer-causing mutations this mechanism is linked to is incredibly high, it’s just a single piece of research – the actual number could be far lower. Indeed, many other researchers think that the correlation between DNA replication errors and cancer touted by this study and the 2015 one is being relied on far too heavily by the authors. Some have pointed out that it is also relying too much on a single data set, and others needed to have been taken into consideration.


Another study, published in Nature back in 2016 by a different group of researchers, came to the very opposite conclusion. They claimed that environmental factors are overwhelmingly the cause of most cancers. The point, really, is that more research needs to be conducted.

In any case, it certainly doesn’t mean that most cancers are completely out of our control. Even if someone’s unlucky enough to be randomly given cancer via these mutations, they are more likely to survive it than at any point in human history, thanks to the incredible work of scientists and medical professionals across the globe.

In fact, the authors of the paper note that if their numbers are accurate, it shows the importance of looking for signs of cancer earlier on in life.

“[Our analyses] accentuate the importance of early detection and intervention to reduce deaths from the many cancers arising from unavoidable mutations,” they write.


The more we learn, the more we realize how much we don't know about cancer. But we're getting there. Creations/Shutterstock

A person’s general risk of getting cancer can be mitigated by moderately exercising, limiting their alcohol intake, having a balanced diet, and cutting out all smoking. In fact, a recent study concluded that cancer deaths in the US could be cut in half if every American adult did these four things.

So don’t panic or buy into the more sensationalist headlines out there. Live a healthy life and donate to cancer research charities. Whether it’s caused by inherited genes, our lifestyle, or plain dumb luck, the more we know, the better we are equipped to push back against it.


healthHealth and Medicine
  • tag
  • cancer,

  • genes,

  • DNA,

  • mutations,

  • risk,

  • cause,

  • environmental,

  • types,

  • random,

  • inherited