8.4: Cancer

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Learning Objectives

Describe the development of cancer.
Identify risk factors for cancer.

Cancer

Cancer is a group of diseases characterized by the uncontrolled growth of abnormal cells. Cancer progresses in 3 stages:

Initiation – cell’s DNA is changed (mutated)
Promotion – mutated cell divides repeatedly
Progression – cancerous cells invade surrounding tissues and spread to other parts of the body

Cancer is triggered by mutations in a cell’s genetic material (initiation). The cause of these changes may be inherited, or it may result from exposure to carcinogens, which are agents that can cause cancer. Carcinogens include chemicals, viruses, certain medical treatments such as radiation, pollution, or other substances and exposures that are known or suspected to cause cancer.

Under normal conditions, a healthy cell will either repair any damage that has been done or self-destruct so that no future cells will be affected. Cells become cancerous when their DNA is damaged, but they do not self-destruct or stop reproducing as normal cells would. As these abnormal cells continue their rapid growth (promotion), in most cancers they come together and form a mass called a tumor. Cancer cells can overwhelm healthy cells and interfere with the healthy functioning of the body. They can also invade other organs and spread throughout the body (progression) in a process known as metastasis.

For even more information about cancer, watch the short (3-minute) video below:

"Cancer 101" by National Geographic

The risk factors for different cancers can vary. For example, exposure to ultraviolet radiation from the sun and from tanning beds is a risk factor for skin cancer, while exposure to asbestos is a risk factor for mesothelioma cancer. Table \(\PageIndex{1}\)^1,2,3 shows some common risk factors for a number of different types of cancer.

Table \(\PageIndex{1}\): Some Risk Factors for Cancer
Unmodifiable Risk Factors	Modifiable Risk Factors
Age. Most cancers occur in people over the age of sixty-five. However, people of all ages, including children, can get cancer. Family history. Certain types of cancer have a genetic link. However, environmental factors may also play a part.	Tobacco. Smoking or chewing tobacco greatly increases the risk for certain cancers, including cancer of the lungs, mouth, and pancreas. Obesity. Linked to cancers of the colon, uterus, pancreas, esophagus, kidney, and breast. Alcohol. Drinking alcohol is linked to cancers of the mouth, throat, esophagus, liver and breast. Red meat and processed meat. The risk of colon cancer seems to increase with the consumption of red meat and processed meat. Physical inactivity. Linked to colon, breast, and other cancers. Viruses or bacteria. Certain viruses or bacteria may increase the risk of developing cancer. For example, Human papillomavirus (HPV), which is sexually transmitted, can cause cervical cancer. Ultraviolet (UV) radiation. UV radiation from the sun and indoor tanning beds is associated with skin cancer.

Signs and Symptoms of Cancer

Signs and symptoms of cancer include:

Unexplained weight loss
Fever
Fatigue
Skin changes
Changes in bowel habits or bladder function
Indigestion or trouble swallowing
White patches inside the mouth or on the tongue
Any thickening or lump

Steps to Reducing the Risk of Cancer

It's estimated that 42% of all cancers are avoidable by managing modifiable risk factors.²

The World Cancer Research Fund and the American Institute for Cancer Research (AICR) have published recommendations for preventing cancer and staying healthy⁴. They include several dietary and lifestyle choices, such as:

be at a healthy weight
be physically active by engaging in at least 150 minutes of moderate physical activity each week (or 75 minutes of vigorous physical activity each week)
eat a diet rich in whole grains, vegetables, fruit, and beans
limit consumption of fast foods and other processed foods high in fat, starches or sugars
limit consumption of red and processed meat
limit consumption of sugar sweetened drinks
limit alcohol consumption
do not use supplements for cancer prevention
for mothers: breastfeed your baby if you can
after a cancer diagnosis follow the recommendations listed here if you can

Antioxidants may work to reduce cancer risk by:

Enhancing the immune system
Preventing oxidative damage to cells
Inhibiting growth of cancer cells
Limiting cancer cells' natural ability to avoid cell death

Key Takeaways

Cancer is a group of diseases characterized by the uncontrolled growth of abnormal cells. As these abnormal cells grow, they can form tumors, interfere with the healthy functioning of the body, and spread throughout the body in a process known as metastasis.
Risk factors for different cancers vary and often include modifiable risk factors that can be managed to reduce risk.
Recommendations for preventing cancer and staying healthy include being physically active, eating healthy foods, and limiting less healthful choices.

References

Risk Factors for Cancer - National Cancer Institute. cancer.gov. https://www.cancer.gov/about-cancer/causes-prevention/risk. Accessed June 29, 2020.
American Cancer Society. Cancer Facts & Figures 2020. Atlanta: American Cancer Society; 2020. Available at https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2020/cancer-facts-and-figures-2020.pdf. Accessed June 29, 2020.
Diet, Nutrition, Physical Activity and Cancer: A Global Perspective. wcrf.org. https://www.wcrf.org/dietandcancer/summary-third-expert-report. Accessed June 29, 2020.
Cancer Prevention Recommendations. wcrf.org. https://www.wcrf.org/dietandcancer/cancer-prevention-recommendations. Accessed June 29, 2020.