2.8.1. What is Cancer?

What Is Cancer?

Cancer is the name given to a collection of related diseases in which the body’s cells begin to divide without stopping and spread into surrounding tissues.

Many cancers form solid tumors, which are masses of tissue. Cancers of the blood, such as leukemias, generally do not form solid tumors.

Cancerous tumors are , which means they can spread into, or invade, nearby tissues. In addition, as these tumors grow, some cancer cells can break off and travel to distant places in the body through the blood or the lymph system and form new tumors far from the original tumour. Each person’s cancer has a unique combination of genetic changes. As the cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.

Unlike malignant tumors, tumors do not invade nearby tissues. However, some benign tumors can be quite large. When removed, they usually do not grow back, whereas malignant tumors sometimes do. Unlike most benign tumors elsewhere in the body, benign tumors in the brain can be life threatening.

More than one hundred diseases are classified as different forms of cancer, all of them characterized by the uncontrolled growth of abnormal cells. Cancer is triggered by mutations in a cell’s genetic material. 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.[1] The National Institutes of Health has classified fifty-four different compounds as known cancer-causing agents in humans.[2]

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, in most cancers they coalesce in 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 in a process known as metastasis. Scientists and the medical community are giving considerable attention to the early stages of cancer, from the moment a healthy cell is exposed to a carcinogen to the point where cells with damaged DNA are replicating out of control. Intervention at any of these early stages could prove to be quite beneficial, because it is thought that most cancers are the result of lifestyle choices and environmental exposure.

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 “The Risk Factors for Cancer” shows some common risk factors for a number of different types of cancer.

Table The 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, bladder, cervix, kidneys, mouth, and pancreas.
  • Alcohol: Drinking alcohol is linked to cancers of the mouth, throat, esophagus, and breast, as well as to cancers of the neck and head.
  • Obesity: Linked to cancers of the colon, uterus, pancreas, esophagus, kidney, and breast.
  • Cooking techniques: Grilling, smoking, and preparing meat at high temperatures forms carcinogens.
  • Red meat:  The risk of colon cancer seems to increase with the consumption of red meat and processed meat.
  • Cured meats:  According to a recent study, there is a mild risk of pancreatic cancer with the consumption of cured meats, such as sausage, pepperoni, bacon, ham, smoked turkey, salami, and hot dogs.
  • Physical inactivity: Linked to colon, breast, and other cancers.
  • Exposure to chemicals: People who have jobs that expose them to chemicals on a regular basis, such as construction workers and painters, have an increased risk of cancer.
  • Viruses or bacteria: Certain viruses or bacteria may increase the risk of developing cancer. For example, human papillomaviruses, which are sexually transmitted, are the primary cause of cervical cancer.

Note: There are numerous risk factors for cancers some of which are modifiable and others of which are not. Source: Cancer

Cancer Statistics

Cancer severely impacts Canadians and societies throughout the world. Cancer is surely the number one cause of death in Canada. Cancer statistics describe what happens in large groups of people and provide a picture in time of the burden of cancer on society. Statistics indicate how many people are diagnosed with and die from cancer each year, the number of people who are currently living after a cancer diagnosis, and the average age at diagnosis. They also reveal differences among groups defined by age, sex, racial/ethnic group, geographic location, and other categories.

Although statistical trends are usually not directly applicable to individual patients, they are essential for governments, policymakers, health professionals, and researchers to understand the impact of cancer on the population and to develop strategies to address the challenges that cancer poses to society. Statistical trends are also important for measuring the success of efforts to control and manage cancer.

Canadian Cancer Stats and Facts: [3]

  • 43% of Canadian women and 45% of Canadian men will develop some type of cancer in their lifetime.
  • 1 in 4 Canadians will die of cancer.
  • The number of new cancer cases is steadily rising in Canada as the population increases in number and age.
  • The risk of developing cancer increases significantly with age.
  • Finding cancer early is imperative. The early you are diagnosed the faster you can receive treatment.
  • In 2019 is was estimated that there would be 220,400 new cases of cancer in Canada with 82,100 people dying from cancer.
  • Lung, colorectal, breast and prostate cancer made up half of all cancer diagnosis in 2019.
  • The most common cancer diagnosis are breast cancer in women and prostate cancer in men.
  • The leading cause of cancer death for both sexes is lung cancer.

Steps to Reducing the Risk of Cancer

On average, 604 Canadians will be diagnosed with cancer every day. On average, 225 Canadians will die from cancer every day.[4]

Although cancer is one of the leading causes of death worldwide, ongoing research and innovations in treatment have improved the outlook for cancer patients to the point where millions now survive or live with cancer, making it a chronic disease.

The American Institute for Cancer Research (AICR) and the Canadian Cancer Society (CCS) have published guidelines for preventing cancer and staying healthy  They include several dietary and lifestyle choices, such as participating in physical activity and maintaining a healthy weight. In addition, AICR and CCS recommends consuming a plant-based diet.[5]

Several epidemiological studies have found a link between eating plenty of fruits and vegetables and a low incidence of certain cancers. Fruits and vegetables containing a wide variety of nutrients and phytochemicals may either prevent or reduce the oxidative damage to cell structures. Cruciferous vegetables, such as cauliflower, broccoli, and brussels sprouts, may also reduce the risk of certain cancers, such as endometrial, esophageal, and others. Also, studies have shown that the more fiber you have in your diet, the lower your risk of colon cancer. [6]

Supplementation may also be helpful to a limited degree. Vitamin D and antioxidants have been linked to lowering the risk of some cancers (however taking an iron supplement may promote others), but, obtaining vital nutrients from food first is the best way to help prevent or manage cancer. In addition, regular and vigorous exercise can lower the risk of breast and colon cancers, among others. Also, wear sunblock, stay in the shade, and avoid the midday sun to protect yourself from skin cancer, which is one of the most common kinds of cancer.[7]


  1. Known and Probable Human Carcinogens. American Cancer Society.http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/GeneralInformationaboutCarcinogens/known-and-probable -human-carcinogens. Updated November 3, 2016. Accessed April 15, 2018.
  2. Israel B. How Many Cancers Are Caused by the Environment?. https://www.scientificamerican.com/article/how-many-cancers-are-caused-by-the-environment. Published May 10, 2010. Accessed April 15, 2018.
  3. Cancer. The Government of Canada. https://www.canada.ca/en/public-health/services/chronic-diseases/cancer.html. Updated on February 10, 2019. Accessed on January 26, 2020
  4. https://www.cancer.ca/en/cancer-information/cancer-101/cancer-statistics-at-a-glance/?region=on
  5. Cancer Prevention and Early Detection Facts and Figures 2013. American Cancer Society. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/cancer-prevention-and-early-detection-facts-and-figures/cancer-prevention-and-early-detection-facts-and-figures-2013.pdf. Published 2013. Accessed April 15, 2018.
  6. https://www.cancer.ca/en/prevention-and-screening/reduce-cancer-risk/make-healthy-choices/eat-well/antioxidants-and-phytochemicals/?region=on
  7. Cancer Prevention: 7 Steps to Reduce Your Risk. Mayo Clinic. http://www.mayoclinic.com/health/cancer -prevention/CA00024. Updated November 29, 2017. Accessed April 15, 2018.


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Fundamentals of Health and Physical Activity by Kerri Z. Delaney and Leslie Barker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.