The development of cancer depends heavily on chance
Around 14 million people worldwide develop cancer each year, and around 8.8 million die of it. Experts repeatedly point out how important it is to maintain a healthy lifestyle in order to reduce the personal risk of cancer. However, researchers are now reporting that bad luck plays a significantly larger role in the development of the disease than previously thought.
Number of new cancer diagnoses doubled in Germany
According to experts, around 14 million people worldwide develop cancer each year and around 8.8 million people die of it. There are also more and more new cancer cases in Germany. The number of new diagnoses in Germany has almost doubled since 1970. According to the Robert Koch Institute (RKI), about one in two Germans will develop it sooner or later.
Many diseases could be avoided
A large part of all cancers are considered preventable. A healthy lifestyle can significantly reduce the risk of cancer. However, US scientists are now reporting that people who get cancer often have bad luck.
The fact that genes and lifestyle play a role in whether someone gets cancer should be largely unchallenged. But chance also has a big impact here. And apparently a larger than previously thought.
According to an analysis by US researchers, two thirds of all cancer mutations are due to random errors in the division of stem cells.
Two thirds of cancers attributed to DNA copying errors
According to the scientists from the Johns Hopkins University in Baltimore in the journal Science, their study suggests that 66 percent of the mutations that cause cancer are due to DNA copying errors, 29 percent to environmental factors and five percent to hereditary factors Mutations.
However, the composition of the three factors varies greatly from cancer to cancer. In tumors of the prostate, brain and bones, 95 percent of the mutations are based on random errors, and 77 percent in the pancreas.
With lung cancer, on the other hand, environmental factors - especially smoking - determine about 65 percent of the mutations.
According to the authors, several mutations must come together before a tumor develops. Most of the changes in DNA have no consequences.
But there is no doubt that around 40 percent of all cancer cases are avoidable. "Our studies do not contradict classic epidemiology, they rather complement it," reports the team.
"It is known that we have to avoid environmental factors such as smoking to reduce the risk of cancer," said biostatist Cristian Tomasetti in a statement from his university.
“What is less known is that a normal cell that divides and copies its DNA makes several mistakes every time,” says the scientist.
Patients are not always to blame for their illness
A publication by the same researchers had caused a lot of discussion two years ago. One of the main criticisms at the time was that the influence of random mutations had become too prominent.
The authors were also accused of methodological errors. At that time, only data from the United States and common types of cancer such as breast or prostate cancer were included.
The current study now has figures on the incidence of 32 different types of cancer from 69 countries in which two thirds of the world's population live.
According to this, some types of cancer can occur "no matter how perfect the environment is," said oncologist Bert Vogelstein.
This could be a small consolation for patients who develop cancer despite a healthy lifestyle. "It is not their fault," said the doctor. "There's nothing behind the disease that they did or didn't do."
Two forms of cancer prevention
The study authors recommend two forms of cancer prevention: For types of tumor in which the environment plays an important role, tips should be given for prevention. In contrast, good early detection is required for tumors, which depend in particular on chance.
When it comes to cancer prevention measures, the fight against smoking is mentioned above all.
Another way to reduce personal cancer risk is to limit alcohol consumption. According to scientific evidence, alcohol can cause seven different types of cancer.
Furthermore, it is recommended to pay attention to a healthy diet, exercise regularly and avoid obesity. According to a recent study, the latter increases the risks of eleven cancer diseases.
Most mutations probably don't matter
"An understanding of the cancer risk that bad luck would ignore would be as inappropriate as one that would not take environmental and genetic factors into account," said Martin Nowak of Harvard University in a "Science" commentary.
“The first analysis by Tomasetti and Vogelstein has caused a lot of discussion, and the new results will do the same. The results show a clear need to understand cancer with mathematical precision. ”
Andreas Trumpp from the German Cancer Research Center (DKFZ) in Heidelberg obviously sees it similarly. "Mathematically, we do not yet understand the development of a tumor in detail," said the expert, according to a message from the dpa news agency. "So far, the data situation is too thin."
However, the study suggests that the number of stem cell divisions has a major impact on cancer risk. "Most mutations probably don't matter," said Trumpp.
"But if a stem cell mutation affects an important gene, it may be passed on to billions of offspring for life and can be the seed for cancer."
Ultimately, it depends on the type of tumor how big the role of the environment, genetic factors and cell division is. (ad)