Risk factors for developing cancer

Although it is usually not possible to determine with certainty the exact cause of cancer in an individual patient, scientific research has identified several risk factors for certain types of cancer that increase the risk of developing the disease. There are also some protective factors that reduce the chance of developing cancer in some people. The aforementioned scientific research is conducted by epidemiologists and is carried out on large populations (numbers) of people, and the differences between people who have the disease and those who do not are sought. A large part of the risk factors can be influenced (environmental and lifestyle factors, e.g. smoking, alcohol, physical activity), while others, such as age, the occurrence of the disease in the family and race, cannot be influenced. The occurrence of cancer in the family can potentially be a sign of a hereditary syndrome associated with cancer. It is important to note that the presence of a risk factor in a person does not mean that the person will necessarily develop cancer, nor is a person without risk factors completely protected, but there can be significant differences in the likelihood of developing the disease. Therefore, by reducing exposure to those risk factors that we can influence, we can significantly reduce the risk of developing cancer. Some risk factors, such as age, are common to many types of cancer, but each type also has its own specific risk factors (eg smoking for lung cancer, HPV for cervical cancer, etc.). Some of the most researched risk factors are listed below.

Age. Age is the most important risk factor for developing cancer in general. As a person ages, more changes (mutations) in DNA accumulate, some of which may be linked to the development of cancer. Older people also tend to have a less effective immune system to fight the disease. In general, about 70% of newly diagnosed cases of cancer occur in people over 60 years of age. This highlights the importance of regular health check-ups. Similar data can be obtained when looking at specific types of cancer separately. For example, the median age of diagnosis for breast cancer is 61 years, for colon cancer 68 years, for lung cancer 70 years, and for prostate cancer 66 years. However, the disease can occur at any age. For example, bone cancer most often occurs in people under 20 years of age, and 10% of leukemia occurs in children and adolescents. Some tumors, such as neuroblastoma, are more common in children than in adults.

Alcohol. Excessive alcohol consumption can increase the risk of developing oral cavity, pharynx, esophagus, larynx, liver and breast cancer. The risk is higher with higher consumption, and it is additionally increased in people who smoke. Accordingly, moderate alcohol consumption is recommended, up to 1 drink per day for women and up to 2 drinks for men. There is evidence that some substances in red wine, such as reservatrol, may have anti-tumor properties, however, there is no scientific research to confirm the above claim.

Chemicals. A wide range of chemicals and other substances can damage DNA and cause cancer. Some are easy to avoid (e.g., quitting smoking), but others are often impossible, such as those in the air, food, water, or materials in the workplace. Some of the known carcinogens include aflatoxin, arsenic, asbestos, benzene, beryllium, cadmium, ethylene oxide, formaldehyde, radon, trichloroethylene, and wood dust.

Image 1. Smoking and excessive alcohol consumption are the most important risk factors for developing cancer. People who both smoke and drink have an additional increased risk that is greater than the pure sum of the risks for smoking and alcohol alone.

Chronic inflammation. Inflammation is a normal physiological process that allows damaged tissue to heal. The inflammatory process begins with the release of chemicals from damaged tissue, to which white blood cells respond by producing substances that stimulate cell growth and division to repair the tissue. Once the damage has been resolved, the inflammation stops. In chronic inflammation, however, the inflammatory process can begin without any tissue injury present, and does not spontaneously end when it should. It can be caused by unresolved infections, an abnormal immune response, or other conditions such as obesity. Over time, increased cell growth and division can cause DNA damage. For example, people with ulcerative colitis or Crohn's disease have an increased risk of developing colon cancer. Several studies have investigated whether anti-inflammatory drugs such as aspirin can reduce the risk of cancer, but the results are not yet completely clear.

Nutrition. Read more about the connection between diet and cancer in a separate article.

Hormones. Estrogens, a group of female sex hormones, are known carcinogens. Although these hormones play an important physiological role in both sexes, they have also been linked to the development of some types of cancer. For example, taking combined hormone therapy for menopause (estrogen + progestin) may increase the risk of developing breast cancer, and estrogen-only preparations increase the risk of developing uterine cancer and are recommended only in women who have had their uterus surgically removed. Studies have shown that the risk of developing breast cancer is related to the production of estrogen and progesterone in the ovaries, and exposure to hormones over a longer period of time (e.g. early menstruation, late menopause, late first pregnancy) or elevated hormone levels increase the risk of the disease. On the other hand, women who have given birth have a lower risk of being barren (a protective factor).

Immunosuppression. Many people who have transplanted organs take medications that suppress the immune system to prevent rejection of the organ. The unfortunate consequence of this is that the immune system cannot effectively fight cancer with these medications. Immunosuppression can also occur with HIV infection, and AIDS patients are also at increased risk of cancer. Overall, the most common malignant tumors in people with transplanted organs are non-Hodgkin lymphoma, lung, kidney, and liver cancer. Non-Hodgkin lymphoma can be caused by infection with the Epstein-Barr virus, and liver cancer by chronic hepatitis B or C infection. Lung and kidney cancers are generally not associated with infections.

Infections. Read more about the role of viruses, bacteria and parasites in the development of cancer in a separate article.

Obesity. Obese people have an increased risk of developing several types of cancer, including breast, colon, uterine, esophageal, kidney, pancreatic, and gallbladder cancer. In contrast, a healthy diet, physical activity, and maintaining a normal body weight can reduce the risk of some types of cancer (protective effect). In addition, such behavior also reduces the risk of developing other diseases, such as heart disease, type 2 diabetes, and high blood pressure.

Radiation. Ionizing radiation is a type of radiation that has enough energy to damage DNA and cause cancer, and includes radon, x-rays, gamma rays, and other high-energy radiation sources. Lower-energy radiation, such as visible light and that produced by mobile devices, has not yet been linked to the development of cancer. Radon is a radioactive gas released by rocks and soil, and is formed by the breakdown of the radioactive element radium. It has been proven that it can cause lung cancer, and there are home tests to measure its concentration. X-rays, gamma rays, alpha particles, beta particles, and neutrons represent high-energy radiation and can cause cancer, and their release can occur in nuclear disasters or when atomic weapons are used. Of course, some diagnostic procedures such as X-rays, CT scans, and PET scans also use such forms of radiation, but the doses are significantly lower and the benefits for the patient always outweigh the potential risks. In the therapeutic use of radiation (radiotherapy), the doses are much higher, and there is a possibility (although small) of the appearance of other tumors after treatment.

Sunlight. The sun and tanning beds are both natural and artificial sources of ultraviolet (UV) radiation. Exposure to UV rays causes premature aging of the skin and damage to the skin, which can ultimately lead to cancer. Accordingly, people of all ages should limit their exposure to strong sunlight (10 a.m. - 4 p.m.) and avoid using tanning beds. It is important to remember that sand, water, snow, and ice reflect UV rays, and they can pass through glass and light clothing. Although skin cancer is more common in people with lighter skin tones, anyone can develop skin cancer, regardless of their skin tone.

Smoking. Smoking is the leading cause of cancer and cancer-related death. Active and passive smokers (people who live with people who smoke) have an increased risk of developing cancer because cigarette smoke contains many carcinogenic chemicals. Smoking has been linked to many types of cancer, including lung, larynx, oral cavity, esophagus, pharynx, bladder, kidney, liver, stomach, pancreas, colon, cervix, and acute myeloid leukemia. People who sniff or chew tobacco have an increased risk of developing oral cavity, esophagus, and pancreatic cancer. There is no safe lower limit for tobacco use, and all smokers are strongly advised to quit smoking. People who quit smoking, regardless of their age, have significant health benefits and an increased life expectancy compared to smokers. Also, quitting smoking when diagnosed with a malignant disease reduces the risk of death.

Additional interesting facts

It is believed that about half of all cancer deaths could be prevented by relatively simple measures , namely by eliminating those risk factors that we can directly influence by changing our behavior. These include quitting smoking and getting vaccinated against HPV. In translation, this would mean saving between 2.5 and 3.5 million lives per year.

"My grandfather smoked his whole life and he was fine," is one of many examples of self-deceiving statements made by smokers. Of course, not all smokers will get lung cancer, nor are non-smokers 100% protected. However, 90% of lung cancer cases occur in smokers . It is estimated that 50 million people have died from smoking in the last 10 years.

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The role of nutrition in the development of cancer

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