Cancer is a term used to describe a large group of diseases characterized by the uncontrolled growth and spread of abnormal cells. These cells have the potential to invade surrounding tissues and spread to other parts of the body, a process known as metastasis. This article provides an overview of cancer, its causes, risk factors, prevention strategies, early detection, and treatment options.
Overview
Cancer can affect any part of the body and is also referred to as malignant tumors or neoplasms. The defining feature of cancer is the rapid creation of abnormal cells that grow beyond their normal boundaries. When these cells spread to other organs, they can cause severe complications and are the primary cause of death from cancer.
Types of cancer
Cancer is one of the leading causes of death worldwide. In 2023 alone, nearly 20 million people died from cancer. The most common types of cancer in terms of new cases diagnosed in 2023include:
- Breast cancer: 2.26 million cases
- Lung cancer: 2.21 million cases
- Colon and rectum cancer: 1.93 million cases
- Prostate cancer: 1.41 million cases
- Skin cancer (non-melanoma): 1.20 million cases
- Stomach cancer: 1.09 million cases
Leading Causes of Cancer Deaths
In 2020, the most common causes of cancer-related deaths were:
- Lung cancer: 1.80 million deaths
- Colon and rectum cancer: 916,000 deaths
- Liver cancer: 830,000 deaths
- Stomach cancer: 769,000 deaths
- Breast cancer: 685,000 deaths
Approximately 400,000 children develop cancer each year, with the most common types varying by country. In 23 countries, cervical cancer is the most common form of cancer.
Causes of Cancer
Cancer develops from the transformation of normal cells into tumor cells through a multi-stage process. This process often progresses from a pre-cancerous lesion to a malignant tumor. The changes in cells that lead to cancer are caused by the interaction between an individual’s genetic factors and external agents. These external agents can be categorized into three main groups:
- Physical carcinogens: This includes ultraviolet and ionizing radiation.
- Chemical carcinogens: Examples include asbestos, components of tobacco smoke, alcohol, aflatoxin (a food contaminant), and arsenic (a contaminant in drinking water).
- Biological carcinogens: Infections from certain viruses, bacteria, or parasites can also lead to cancer.
The World Health Organization (WHO), through its cancer research agency, the International Agency for Research on Cancer (IARC), maintains a classification of cancer-causing agents.
The Role of Age in Cancer
The likelihood of developing cancer increases with age. This is likely due to the accumulation of risks for specific cancers over time, combined with a decline in the effectiveness of cellular repair mechanisms as a person ages.
Risk Factors for Cancer
Several factors can increase the risk of developing cancer, including:
- Tobacco use
- Alcohol consumption
- Unhealthy diet
- Physical inactivity
- Air pollution
Chronic infections are also significant risk factors for cancer, particularly in low- and middle-income countries. In 2018, approximately 13% of cancers diagnosed globally were attributed to carcinogenic infections, such as Helicobacter pylori, human papillomavirus (HPV), hepatitis B virus, hepatitis C virus, and Epstein-Barr virus.
Prevention of Cancer
It is estimated that between 30% and 50% of cancers can be prevented by avoiding risk factors and implementing evidence-based prevention strategies. Here are some ways to reduce the risk of cancer:
- Avoid tobacco use.
- Maintain a healthy body weight.
- Eat a healthy diet that includes fruits and vegetables.
- Engage in regular physical activity.
- Limit alcohol consumption.
- Get vaccinated against HPV and hepatitis B if recommended.
- Avoid excessive exposure to ultraviolet radiation, both from the sun and artificial sources.
- Ensure safe use of radiation in healthcare settings.
- Minimize occupational exposure to ionizing radiation.
- Reduce exposure to outdoor and indoor air pollution.
Early Detection of Cancer
Early detection is critical for reducing cancer mortality. When cancer is identified and treated early, it is more likely to respond to treatment, increasing the chances of survival. There are two main components of early detection: early diagnosis and screening.
Early Diagnosis
Early diagnosis involves recognizing the symptoms of different cancers and seeking medical advice when abnormalities are observed. Key components of early diagnosis include:
- Awareness of cancer symptoms.
- Access to clinical evaluation and diagnostic services.
- Timely referral to treatment services.
Early diagnosis is crucial for most cancers, and cancer programs should aim to reduce delays and barriers to diagnosis and treatment.
Screening
Screening aims to identify individuals with signs of specific cancers or pre-cancerous conditions before they develop symptoms. If abnormalities are detected during screening, further tests should be conducted to confirm the diagnosis, followed by appropriate treatment if cancer is present.
Screening programs are effective for certain cancers but are complex and resource-intensive. Even in settings where screening programs exist, early diagnosis is still necessary to identify cancer cases in individuals who do not meet the age or risk factor criteria for screening. Screening methods are typically based on age and risk factors to avoid excessive false-positive results. Examples of screening methods include:
- HPV tests for cervical cancer.
- Mammography for breast cancer in women aged 50-69 in well-resourced health systems.
Treatment of Cancer
Accurate cancer diagnosis is essential for determining the appropriate and effective treatment. Treatment options often include surgery, radiotherapy, and/or systemic therapies such as chemotherapy, hormonal treatments, and targeted biological therapies. The selection of a treatment regimen depends on the type of cancer and the individual patient’s condition. Completing the treatment protocol within a defined period is crucial for achieving the best therapeutic outcomes.
Conclusion
Cancer remains a significant global health challenge, with millions of lives affected each year. However, by understanding the causes, recognizing risk factors, implementing prevention strategies, and ensuring early detection and appropriate treatment, the burden of cancer can be significantly reduced. Public awareness, access to healthcare, and ongoing research are vital in the fight against cancer.
