It seems the answer to why some people get cancer and others do not may be the same as why a tornado will hit one house and leave the one next door still standing: pure bad luck.
A study published this month by researchers at Johns Hopkins University in the journal Science found that more than two-thirds of cancer-causing cell mutations are the result of random mistakes in DNA replication that happen during normal cell division. Environmental and lifestyle factors account for 29% of mutations, while the remaining five percent are inherited.
The study authors looked at the genome sequencing and epidemiological data for 32 types of cancer and concluded that the vast majority of cancers are due to random mutations of cells in their normal replication cycle, which happens in the body millions of times a day. They also studied 423 international cancer databases across six continents representing 4.8 billion people (two-thirds of the world’s population) to support their conclusions.
“Every time a perfectly normal cell divides, as you all know, it makes several mistakes—mutations,” one of the study’s authors, Dr. Bert Vogelstein, explained in a briefing. “Now most of the time, these mutations don’t do any harm. They occur in junk DNA, genes unrelated to cancer, unimportant places with respect to cancer. That’s the usual situation and that’s good luck.” But when one of these miscopies occurs in a cancer-causing gene, “that’s bad luck,” he said.
New cells are formed by division, and DNA copies are made in the process. Every DNA copy contains an average of three random mutations. That’s fine, if the mutation occurs in genes that have nothing to do with cancer. It’s also not a problem if the body’s natural defense mechanisms seek out and destroy the mutation in a cancer-related gene.
Another study author, Cristian Tomasetti, explained that just one mutation is not enough to cause cancer; typically three or more mutations must occur to trigger cancer. For example, if your cells miscopy DNA and cause two random mutations as a result, a third mutation is still needed to slide the cell into cancer. Obesity, smoking, lack of exercise, and poor eating habits might supply that necessary third gene defect that tips your body into a disease state, Tomasetti said. Or, a healthier immune system might be better postioned to fight off the mutation.
Nevertheless, this new study flies in the face of accepted wisdom, which has attributed the occurrence of cancer primarily to preventable factors. Unfortunately, this type of thinking has led to a blame-the-victim mentality, even on the part of those who get cancer. And parents of children who develop cancer agonized over how they somehow “gave” their children the disease, either through lifestyle or heredity. This study should serve to put an end to that view that those who contract cancer did something “wrong.”
But another way to look at the results of this study is to reinforce what we in the medical profession have been saying for decades: There is a way to reduce your risk for cancer, and that is through lifestyle modifications.
Think of it: If researchers had developed a drug that would reduce your risk of getting cancer by 30%, it would be considered a major new breakthrough. What this study does is underline the fact that lifestyle still can play a role in reducing your risk.
Thus, your physicians at The Medical Group of South Florida will continue to recommend a healthy lifestyle and regular check-ups as your last line of defense against contracting cancer.