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Cancer risk factors and prevention

Cancer risk factors and prevention

Many agents are classified as carcinogenic in humans by the International Agency for Research on Cancer, an organization that depends on the World Health Organization (WHO) in charge of inherent risk assessment to each identified factor. These factors are related to lifestyle and also to exposure to certain substances. It is therefore possible to exercise prevention against factors that can be controlled in this way (by acting in particular on individual behavior), prevention which is estimated to be able to reduce the number of cancers by 40%.

Tobacco, leading cause of cancer

Tobacco contains more than 70 carcinogens. Smoking is not only implicated in the occurrence of lung cancer; it is also in that of the upper airways, the stomach, the urinary tract, etc. Prevention consists of quitting smoking pure and simple, insofar as even minimal consumption is still considered harmful.

Tobacco is the leading cause of cancer, both in France and worldwide. Similarly, smoking is the number one cause of preventable cancer.

In France, smoking is responsible for more than 35,000 cancer deaths each year, above all of the lung (about 90% of cases). Smoking is thus the leading cause of cancer death in subjects under 65 years of age. It is also involved in 50 to 70% of cancers of the upper aerodigestive tract (nose, mouth, neck, esophagus, etc.).

The increase in the level of risk is linked to the number of cigarettes smoked, and even more to the duration of exposure. This is how we evaluate consumption in pack-years (for example, a subject who has smoked 10 cigarettes a day for 30 years has a consumption of 1/2 pack × 30, i.e. 15 pack-years). Starting to smoke in adolescence carries an additional risk.

All forms of tobacco use are dangerous. This is true of course for cigarettes, but also for cigars, pipes, shisha and even chewing tobacco. Even passive smoking has been blamed for cancers.

It is estimated that with the avoidance of tobacco, we could avoid about a quarter of cancer-related deaths.

Prevention then involves quitting smoking altogether. The sooner this stop occurs, the greater the benefit; the longer the withdrawal, the better the chances of escaping cancer, with the risk almost disappearing after 10 to 15 years of withdrawal.

Alcohol, second leading cause of cancer death

Alcohol consumption is responsible for 8% of cancers, making it the second most preventable cause of cancer death after tobacco.

Indeed, excessive alcohol consumption is implicated in the appearance of many cancers, in particular those of the esophagus and stomach, liver or colorectal cancers.

In addition, it reinforces the carcinogenic effect of other factors, such as tobacco.

The risk of cancer increases with the dose of alcohol consumed and exists even for consumption limited to one drink per day, for example for breast cancer. The risk becomes significant from ten glasses of alcohol per week, which corresponds to the recommendation of “maximum two glasses per day, and not every day”.

Total withdrawal must be required in true alcoholism (defined as dependence on everyday alcohol).

Lifestyle:risk factor and means of cancer prevention

Lifestyle itself can be a risk factor. Factors related to nutrition and physical activity have indeed been identified as increasing the risk of cancer.

Food works on many levels:

  • Obesity or overweight.

Indeed, an increased body mass index (BMI) is associated with an increase in cancer of the breast, pancreas, kidney, colon or esophagus. Nearly 19,000 new cases of cancer in France were attributed to being overweight in 2015, i.e. 5.4% of all new cases of cancer.

  • High consumption of certain foods.

For example, a high consumption of red meat and cold meats is directly associated with colorectal cancers, that of salt and salty foods is made responsible for stomach cancer. Finally, taking food supplements, including beta-carotene, has been implicated in certain cancers, such as lung cancer.

In contrast to these factors which can favor the appearance of cancers, others can on the contrary prove to be protective:

  • Regular physical activity prevents the occurrence of certain cancers such as breast or colon cancer.
  • The consumption of fruits and vegetables can prevent the development of cancers, especially those of the upper aerodigestive tract, stomach and lung. Fruits and vegetables have indeed protective properties thanks to their significant content of vitamins, fibers, and perhaps even more so in antioxidants. Consumption of fiber-rich foods (including pulses and whole grains) is associated with a reduced risk of colorectal cancer.

Breastfeeding, finally, is protective.

It is notable that the nutritional risk factors are globally the same as those implicated in vascular diseases. Geriatricians even believe that they are associated with an increase in Alzheimer's disease as well. Hence the really crucial importance of nutritional prevention.

The sun:protect yourself from it to avoid skin cancer

UVA and UVB rays emitted by the sun are responsible for most skin cancers (about 2/3), and in particular melanomas. However, you could easily protect yourself from the bad effects of these rays by regularly applying sunscreen or by avoiding exposure to the sun during the hottest hours.

These cancers are constantly increasing. Skin melanoma is diagnosed in 15,000 people per year, with an increase of 3% per year over the period 2010-2018.

Contrary to popular belief, the danger does not only come from sunburn.

Two types of UV rays from the sun can reach the skin:

  • UVBs, those responsible for the phenomenon of “sunburn”;
  • UVA rays, which penetrate deeply into the skin but whose effects are not immediately visible.

Both UVA and UVB rays increase the risk of skin cancer. It should be noted that some of these rays are not filtered by glass and you are therefore not necessarily protected behind glass (in a car for example).

To protect yourself, different means exist in addition to protection with a cream, because sunscreen only offers incomplete protection. It should therefore:

  • To protect yourself with clothing (t-shirt, hat) in addition to the cream, because clothing protects against UV rays more effectively than cream;
  • Avoid exposure during the hottest hours, i.e. between noon and 4 p.m. It is during this period, in fact, that the rays are most powerful;
  • Get in the shade;
  • Apply barrier cream regularly, at least once every two hours.

These tips are particularly valid for children and adolescents, who are the most fragile.

Some skins are more sensitive than others. This is the case for people with light skin, and blond or red hair. Indeed these clear phenotypes are more at risk of developing skin cancer.

Finally, people with a large number of moles or a family history of skin cancer are also at risk and should have their skin examined regularly by a dermatologist.

Environmental factors:constant exposure

Many substances commonly found in the everyday environment are carcinogens. Their list is not only non-exhaustive, but is constantly being supplemented. The IARC counts several hundred of them. According to sources, 10 to 30% of cancers are due to these environmental factors.

Some exposures are clearly identified as carcinogenic. This is the case, for example:

  • radon, which increases cases of lung cancer
  • certain pesticides
  • air pollution
  • indoor air pollution of which passive smoking is the most dangerous source

Others are possibly carcinogenic such as very low frequency magnetic fields.

Viruses and bacteria:the role of infectious agents

Some cancers develop from infections by viruses or bacteria, with the particularity in this case of transmissibility, including the sexual route. In reality, strictly speaking, it is not the cancers themselves that are transmissible, but the infectious agents in question.

4% of cancers are linked to infections:

  • Liver cancer:hepatitis B and C viruses
  • Cervical Cancer:Human Papillomavirus (HPV)
  • Cancer of the oropharynx:human papillomavirus (HPV)
  • Non-Hodgkin lymphomas:Epstein Barr virus (EBV), HIV virus
  • Hodgkin's disease:Epstein Barr virus (EBV)
  • Stomach cancer:Helicobacter pylori bacteria
  • Kaposi's sarcoma:HIV virus

Since these cancers are linked to transmissible infections, they may be preventable.

Thus, the use of condoms is effective in the fight against the transmission of sexually transmitted viruses, such as hepatitis B and HIV. The transmission of the human papillomavirus, on the other hand, can be done with sexual practices such as touching with dirty hands or unprotected fellatio. The use of a condom therefore only partially protects.

Vaccination can also be effective. This is the case for hepatitis B and, in part, for the human papillomavirus. The latter, in fact, only offers protection against uterine cancer in 70% to 90% of cases (because there are different types of papillomavirus). This incomplete protection therefore justifies regular screening for cancer of the cervix by a cervico-vaginal smear.

It should be noted that the vaccination against the papillomavirus concerns girls and boys.

Sources

  • National Cancer Institute. Reducing the risk of cancer – Understand, prevent, detect (e-cancer.fr), consulted on August 19, 2021
  • National Cancer Institute. Fact sheet “Primary cancer prevention in France”, June 2015
  • National Cancer Institute. Fact sheet "Benefits of physical activity during and after cancer - From knowledge to practical benchmarks", https://www.e-cancer.fr/Expertises-et-publications/Catalogue-des-publications/Benefices-de-l -physical-activity-during-and-after-cancer-From-knowledge-to-practical-benchmarks March 2017
  • National Cancer Institute. Fact sheet “Smoking cessation and cancer prevention”, May 2011
  • National Cancer Institute. Reference sheet “Pesticides and cancer risks”, July 2014
  • National Cancer Institute. “Occupational cancers” fact sheet, January 2012