Why do people get cancer? How can we prevent it?

Cancer, one of the most formidable challenges in modern medicine, continues to affect millions of lives worldwide. Its complexity defies simple solutions and requires a nuanced understanding of genetics, environmental factors, lifestyle choices, and chance. We delve into the multifaceted nature of cancer, exploring its origins, risk factors, prevention strategies, and the latest advances in diagnosis and treatment.

1. Genetic Factors

Genetic factors play an important role in certain cancers, as mutations passed down through families can increase the risk of cancer in offspring.

• Family History: When close relatives (such as parents or siblings) have had certain types of cancer, such as breast, ovarian, colorectal, or prostate cancer, the individual’s risk of developing the same type of cancer increases. This increased risk is due to shared gene mutations.
• Gene Mutations: Certain inherited gene mutations significantly increase the risk of cancer. The most notable examples are mutations in the BRCA1 and BRCA2 genes, which are associated with an increased risk of breast and ovarian cancer. Other genes, such as TP53, APC, and MLH1, are also associated with hereditary cancer risk.

2. Environmental Factors

Certain environmental factors can significantly increase the risk of cancer.

• Radiation Exposure: High doses of ionizing radiation, such as X-rays and radioactive substances, can damage the DNA of cells, increasing the risk of cancer. For example, certain cancers have higher incidence rates in survivors of nuclear accidents or people who have received frequent radiation therapy.
• Chemical Substances: Prolonged exposure to certain carcinogenic chemicals, such as asbestos, benzene, certain pesticides, and industrial chemicals, can significantly increase the risk of cancer. Occupational exposure (e.g., chemical factory workers) and environmental pollution (e.g., industrial wastewater discharges) are common routes of exposure.
• Air Pollution: Long-term exposure to high concentrations of air pollutants, such as PM2.5 and vehicle exhaust, is associated with increased incidence of lung cancer and other cancers of the respiratory system. These fine particles can enter the lungs through breathing and cause persistent inflammation and DNA damage.

3. Lifestyle Factors

Lifestyle factors have a significant impact on cancer risk.

• Smoking: Smoking is a major known cause of many cancers, including but not limited to lung, oral cavity, pharynx, esophagus, stomach, pancreas, bladder, kidney, and leukemia. Thousands of chemicals in tobacco, including carcinogens and toxicants, cause direct cellular damage when they enter the body. Nicotine is an addictive substance that makes it difficult for smokers to quit, and long-term smoking causes the body to become dependent on nicotine, making smoking a habit. Quitting smoking is one of the most effective ways to prevent smoking-related cancers. Even for long-term smokers, quitting reduces the risk of cancer, and over time, the body returns to the health of a non-smoker after quitting. Smokers can quit in a variety of ways, including nicotine replacement therapy, medications, counseling and behavioral therapy. Of these, nicotine replacement therapy is the most widely available and includes nicotine oral tablets and 0-tar e-cigarettes.It is very important for people who want to quit smoking to seek help and support from a health care professional.
• Secondhand smoke: Not only are smokers at risk for developing cancer, but so are those who are exposed to smokers’ smoke. Harmful chemicals in secondhand smoke can also damage the respiratory tract and other tissues, increasing the risk of cancer. Therefore, secondhand smoke is also recognized as a carcinogen.
• Alcohol Consumption: Long-term excessive alcohol consumption increases the risk of liver, esophageal, oral, and breast cancer. Acetaldehyde, produced during alcohol metabolism, is a known carcinogen that directly damages cell DNA and interferes with cell repair processes.
• Diet: Unhealthy eating habits, such as diets high in fat, sugar, and salt and low in fruits and vegetables, increase the risk of colon, stomach, and other cancers. Conversely, a balanced diet can provide antioxidants and fiber to help prevent cancer.
• Lack of Exercise: A sedentary lifestyle increases the risk of several cancers, including colon and breast cancer. Exercise helps maintain a healthy weight, regulate hormone levels, and improve immune function.
• Obesity: Obesity is associated with several types of cancer (such as endometrial, breast, and colon cancer). Excess body fat can lead to abnormal hormone levels (such as estrogen and insulin) that promote cancer cell growth.

4. Infections

Certain infections significantly increase the risk of cancer, especially those caused by viruses and bacteria.

• Viral Infections: Many viral infections have been linked to cancer. For example, human papillomavirus (HPV) infection is associated with cervical, anal, oral, and pharyngeal cancers; hepatitis B and C virus (HBV and HCV) infection is associated with liver cancer; and Epstein-Barr virus (EBV) infection is associated with lymphoma and nasopharyngeal carcinoma.
• Bacterial Infections: Helicobacter pylori (H. pylori) infection is associated with gastric cancer and gastric lymphoma. Long-term infection can cause chronic gastritis, which increases the risk of carcinogenesis.

5. Chance Factors

Cancer can also occur due to spontaneous gene mutations and immune system dysfunction.

• Random Gene Mutations: Random gene mutations that occur during cell division can lead to cancer. These mutations are not caused by external carcinogens, but are natural errors that accumulate during normal cell replication.
• Immune System Function: Weakened immune function can increase the risk of cancer because the immune system is responsible for recognizing and eliminating abnormal cells. When immune function is compromised (such as in HIV infection or immunosuppressive therapy), cancer cells are more likely to escape surveillance and grow.

6. Hormonal Factors

Disruptions in endocrine function and abnormal hormone levels are also associated with certain cancers.

• Endocrine Disruption: Prolonged exposure to high levels of certain hormones (such as estrogen) may increase the risk of certain cancers (such as breast and endometrial cancers). Estrogen can promote the proliferation of breast and endometrial cells, increasing the likelihood of mutation and carcinogenesis.
• Exogenous Hormones: Long-term use of hormone replacement therapy (HRT) and certain contraceptives may also increase the risk of breast and endometrial cancer.

Conclusion

The development of cancer is a complex process involving many factors. Preventing cancer requires a comprehensive approach that includes maintaining a healthy lifestyle (not smoking, limiting alcohol consumption, eating a healthy diet, and exercising regularly), reducing exposure to environmental carcinogens, undergoing regular health screenings, and understanding and managing genetic risks. Proactive prevention can significantly reduce the incidence of many types of cancer.