What causes cancer

Overview

Cancer develops when cells in the body undergo genetic mutations that cause them to grow uncontrollably and invade other tissues. These mutations accumulate over time, typically requiring multiple changes before cancer develops. Understanding the causes helps with prevention and early detection strategies.

Environmental Risk Factors

Environmental exposures significantly increase cancer risk. Tobacco smoke remains the single most preventable cause of cancer, accounting for approximately 30% of cancer deaths. Secondhand smoke exposure also increases risk for non-smokers. Ultraviolet radiation from sun exposure is the primary cause of skin cancer, including melanoma. Occupational exposures to asbestos, radon, and certain chemicals increase lung and other cancers.

Infections and Viruses

Certain pathogens increase cancer risk by causing chronic inflammation or directly damaging DNA. Human papillomavirus (HPV) causes cervical, anal, and throat cancers. Hepatitis B and C viruses lead to liver cancer. Helicobacter pylori bacteria increases stomach cancer risk. These infection-related cancers are often preventable through vaccination or treatment.

Lifestyle and Dietary Factors

Lifestyle choices significantly influence cancer development. Obesity increases risk for breast, colon, endometrial, and pancreatic cancers. Alcohol consumption, especially excessive intake, increases breast, liver, and esophageal cancer risk. Diets high in processed red meat increase colorectal cancer risk, while diets low in fruits and vegetables provide fewer protective compounds. Regular physical activity reduces cancer risk.

Genetic and Age-Related Factors

Genetics play a significant role in cancer susceptibility. While 85-90% of cancers result from acquired mutations during lifetime, inherited mutations like BRCA1 and BRCA2 substantially increase breast and ovarian cancer risk. Age is a fundamental risk factor—cancer cells develop over decades as mutations accumulate. Most cancers occur in people over 50 years old.

Prevention and Risk Reduction

Many cancers can be prevented or risk significantly reduced through lifestyle modifications. Avoiding tobacco and limiting alcohol are critical. Using sunscreen and protective clothing reduces skin cancer risk. Maintaining healthy weight, eating fiber-rich diets with abundant fruits and vegetables, exercising regularly, and getting vaccinated against cancer-causing viruses all help prevent cancer development.