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.