Most cancers not caused by genes or lifestyle but bad luck

Image: The Telegraph

Image: The Telegraph

Researchers at the Johns Hopkins University School of Medicine in the US have discovered that the majority of cancers are not the result of our environment or lifestyles, but in fact bad luck.

This goes against the general medical view held for decades, that people are somehow responsible for an increased risk of contracting certain cancers by poor lifestyles choices.

The research, which was published in the Journal Science, found that mistakes when cell are dividing accounted for more than two thirds of cancers, and this explained why some cancers are more common than others.

For example, where cells in the body have to divide more frequently you are more likely to get random mistakes, which is why colon cancer is so prevalent, as these cells divide twice as quickly as those in the upper bowel. Equally, the cells of the pancreas divide faster than those of the pelvis, which is why more people suffer from pancreatic cancer than pelvic cancer.

Scientists at the university studied 31 types of cancer, and found that only nine could be linked specifically to poor lifestyle choices or faulty genes. The rest were simply a case of bad luck.  The results have led these researchers to emphasize that more care and attention should spent on diagnosis, rather than genetic screening or prevention through lifestyle changes.

“If two-thirds of cancer incidence across tissues is explained by random DNA mutations that occur when stem cells divide, then changing our lifestyle and habits will be a huge help in preventing certain cancers, but may not be as effective for a variety of others,” said Dr Cristian Tomasetti.

“We should focus more resources on finding ways to detect such cancers at early, curable stages.”

Cells are always dividing in the body in order to renew and repair any damage, but sometimes during the course of some division a mistake is made in which one letter of the DNA strand is swapped and it is this mutation that causes cancer to start growing.

The study discovered that the more these mutations occurred, the higher the rate of cancer, which indicated that it was these internal errors, rather than external forces, that encouraged the cells to multiply so quickly.

Lead researcher Professor Bert Vogelstein, said: “Cancer-free longevity in people exposed to cancer-causing agents, such as tobacco, is often attributed to their ‘good genes,’ but the truth is that most of them simply had good luck.

“Our study shows, in general, that a change in the number of stem cell divisions in a tissue type is highly correlated with a change in the incidence of cancer in that same tissue.

“We found that the types of cancer that had higher risk than predicted by the number of stem cell divisions were precisely the ones you’d expect, including lung cancer, which is linked to smoking; skin cancer, linked to sun exposure; and forms of cancers associated with hereditary syndromes.”

Other health experts were keen to point out the benefits of adapting a healthy lifestyle:

“While some genetic mistakes are due to bad luck, we know that our cancer risk depends on a combination of our genes, our environment and other aspects of our lives, many of which we can control,” said Dr Emma Smith, senior science information officer at Cancer Research UK.

“We estimate that more than four in 10 cancers could be prevented by lifestyle changes, like not smoking, keeping a healthy weight, eating a healthy diet and cutting back on alcohol.  Making these changes is not a guarantee against cancer, but it stacks the odds in our favour. It’s vital that we continue making progress to detect cancer earlier and improve treatments.”

There are people who hold the opinion that those who smoke or indulge in an unhealthy lifestyle should opt out of the healthcare system, or pay for themselves, perhaps this research may go some way to appeasing these negative views. An opinion shared by Prof Hans Clevers, a stem cell and cancer biologist at the Hubrecht Institute in Utrecht, the Netherlands, who said:

“The average cancer patient is just unlucky.”

Source: The Telegraph