Facts on Preventing Cancer The Cancer Process

Transcription

1 Facts on Preventing Cancer The Cancer Process

2 The Cancer Process How does the transformation of a single cell into cancer occur? And how does your body work to slow the cancer process down? This brochure explains what cancer is and what you can do to protect yourself against it. Throughout our lives, everyday habits such as what we eat, whether we smoke and how active we are all contribute to our risk of developing cancer. The more unhealthy lifestyle factors we engage in, the greater likelihood that our cells can sustain damage that leads to cancer. This brochure is based on the AICR/ WCRF expert report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective, and its ongoing review and update through our Continuous Update Project (CUP). The expert report was written by a panel of leading scientists and researchers who reviewed all the available evidence on diet, physical activity and weight management in relation to cancer prevention and survivorship. The expert report contains recommendations that scientists estimate could help prevent about one-third of the most common cancers, such as colon and breast cancer. (See page 14 for the full list of AICR Recommendations for Cancer Prevention.) Words in blue boldface type appear in the Glossary on page 10. What is Cancer? Cancer originates at the cell level. Cells are the basic building blocks of our body. Every cell contains genetic information (DNA), which controls its functions. The body is made up of many types of cells that compose different organs. Normally, these cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they are programmed to die and are replaced with new cells. Cancer occurs when abnormal cells divide without stopping because of permanent changes, called mutations, in DNA. These abnormal cancer cells do not die when they should and new cells form and grow uncontrolled. Cancer cells often form a mass called a tumor. Not all tumors are cancerous; tumors can be benign or malignant. Benign tumors aren t cancerous. They are different from malignant tumors because they do not spread to other parts of the body. They are slow growing as opposed to rapidly growing cancerous tumors, and the edges of their cells are clearly defined. 1

3 Benign tumors can often be removed; examples are moles and uterine fibroid tumors. In most cases, they do not come back. Malignant tumors are cancerous. Cells in these tumors change shape and grow rapidly. They can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis. There are more than 100 different types of cancer. Most are named for the organ or type of cell in which they start. The main categories of cancer include: Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels or other connective or supportive tissue. Whether cancer cells divide quickly or slowly, they ultimately disrupt the normal structure and function of the body s normal tissue. Cancers are capable of spreading throughout the body by two mechanisms: invasion and metastasis. Invasion refers to the direct migration and penetration by cancer cells into neighboring tissues. Metastasis refers to the condition where cancer cells circulate through the bloodstream and then invade normal tissues elsewhere in the body. When cancer is found, a doctor will determine what type it is and how fast it is growing. He or she will also determine whether cancer cells have invaded nearby healthy tissue or spread (metastasized) to other parts of the body. In some cases, finding cancer early may decrease a person s risk of dying from the cancer. For this reason, improving screening methods for early detection is currently a high priority for cancer researchers and healthcare providers. Leukemia - cancer that starts in bloodforming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and myeloma - cancers that begin in the cells of the immune system. Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord. 2 3

4 What Causes Cancer? The DNA of a cell can become damaged or changed by external factors in the environment or by inherited genes. Obesity Diet low in vegetables, fruits, whole grains and beans High red and processed meat consumption Lack of physical activity Excessive alcohol and sodium consumption Healthy Cell Healthy, stable weight Plenty of vegetables, fruits, whole grains and beans At least 30 minutes of moderate activity each day Breastfeeding It usually takes years, even decades, for DNA damage to turn into cancer. Many changes need to occur for the disease to develop. But there are steps you can take now to prevent, delay or even stop the cancer process. For example: Don t smoke or chew tobacco. Smoking by itself causes 90 percent of lung cancer deaths among men and 80 percent of lung cancer deaths among women; and 40 percent of all cancers. Maintain a healthy weight for you. After not smoking, being a healthy weight is the most important way you can reduce your risk of cancer. Extra fat tissue, especially around the waist, is an indicator of higher risk of cancer (see Inflammation, on p. 7). Limit alcohol. Drinking alcohol can cause cancers of the breast, colorectum (in men), mouth, throat, esophagus and liver. Avoid processed meats (such as hot dogs, bologna, sausage, bacon and ham). They are strongly linked to risk for colon cancer, as is eating more than 18 ounces of cooked red meat (including beef, pork and lamb) per week. Cancer Cell Healthy Cell Genetic Causes Only 5-10 percent of all cancers are associated with having a family history of cancer. People who inherit these genes do have a higher cancer risk, but may never develop the disease. 4 5

5 If you have a family history of cancer and are concerned, it s important to consult your healthcare provider and get regular screenings. Environmental factors Known environmental cancer risks include: Too much exposure to the sun Cigarette smoke (including second hand smoke) Certain industrial chemicals affecting workers with high exposures to them Many environmental factors such as pollution and cigarette smoke contain carcinogens. They also create molecules called free radicals. These molecules occur naturally inside the body as we age. Although these molecules do some good, too many may cause damage that increases cancer risk. Plant-based foods vegetables, fruits, whole grains and beans contain vitamins and phytochemicals that often act as antioxidants, which can protect the cell and DNA from damage due to free radicals. Radiation therapy If you have had radiation therapy in the past, it may have put you at higher risk for other cancers. Radiation therapy for cancer can damage DNA and increase the number of mutations affecting cells. Infectious diseases Several viruses lead to certain cancers: Epstein Barr virus in esophageal cancer, Helicobacter pylori virus in stomach cancer, hepatitis B and C viruses in liver cancer, and Human papilloma virus in cervical cancer. Inflammation Although acute inflammation is the body s response to infection or injury and is essential to healing, too much constant, or chronic, inflammation can damage cells and their DNA. Because fat cells constantly make certain proteins that can lead to inflammation, overweight and obesity are strongly tied to higher cancer risk, as well as heart disease and diabetes. Insulin resistance This condition occurs when cells do not respond properly to insulin, a hormone produced by the pancreas that helps cells take in and use glucose (a form of sugar in the blood that increases after we eat) needed to produce energy. The body tries to make up for this by producing more insulin. If untreated, insulin resistance can lead to Type 2 diabetes and is associated with increased risk of some cancers. 6 7

6 What Protects Us From Cancer? A healthy diet and adequate physical activity reduce cancer risk. AICR/WCRF s expert panel estimates that approximately one-third of the most common cancers could be prevented if everyone followed the AICR Guidelines for Cancer Prevention: Choose mostly plant foods, limit red meat and avoid processed meat, as well as highly processed foods and beverages with added sugar and fat. For protection from cancer, eat an abundant variety of vegetables, fruits, whole grains and beans. Plant foods contain vitamins, minerals, fiber, antioxidants and phytochemicals (naturally occurring compounds) that block the beginning and growth of cancer. Be physically active every day in any way for 30 minutes or more. Strong scientific evidence shows that physical activity protects against colon cancer and probably protects against breast and endometrial cancers. Physical activity reduces excess levels of hormones that may stimulate cancer growth. AICR recommends moving often during the day to avoid being sedentary for too long. Aim to be a healthy weight throughout life. Obesity and overweight are linked to postmenopausal breast cancer, colon cancer and cancers of the endometrium, esophagus, gallbladder, kidney and pancreas. Excess body fat can raise hormone levels, including substances called growth factors that may speed up the cancer process. Prevent weight gain by controlling portion sizes, eating foods Visit for plenty of great ideas for healthy foods, physical activity and weight management advice. that are lower in calories and getting regular physical activity. And always remember do not smoke or chew tobacco. Smoking is the single most common cause of cancer, according to the National Cancer Institute. YOU are in control of many of the most important cancer risk factors. For more information, visit For mothers and their babies, breastfeeding has many benefits, including protection against cancer. Breastfeeding reduces the levels of some hormones linked to cancer, such as estrogen. Babies who are breastfed are less likely to become overweight and obese later in childhood. It is best for mothers to breastfeed their babies exclusively for the first six months of life. 8 9

7 Glossary Antioxidants - Substances that can protect the cell and DNA from the damage caused by free radicals. Benign - Harmless; describes a non-cancerous tumor. Carcinogen - Any substance that can cause cancer. Used to describe compounds that increase the risk of getting cancer by damaging DNA directly in the cell. Cell - Basic structural and functional building block of our body and other living organisms. DNA - Deoxyribonucleic acid, the carrier of genetic information, present in every cell of the body. Epstein Barr virus - A member of the herpes virus family that can lead to esophageal cancer. Free radicals - Harmful molecules created in the body as a byproduct of normal cellular activity. Environmental factors such as pollution and cigarette smoke can also produce free radicals. If produced in large numbers, they can start a chain reaction, which leads to cellular and DNA damage. Growth factors - Substances in the body that increase cellular growth. Some are necessary for proper human growth. In some circumstances, however, they can stimulate cancer growth. Helicobacter pylori - A bacterium, also known as H. pylori, that causes inflammation and damage to cells lining the stomach and small intestine and is a known cause of stomach cancer. Hormones - Substances that are secreted by cells or glands in our bodies and facilitate several functions. However, high levels of certain hormones can raise cancer risk. Examples of hormones include estrogen, androgen and testosterone, growth factors and insulin, which is produced in the pancreas to regulate the amount of glucose (sugar) in the blood. Human papilloma virus - An established cause of cervical cancer. Inflammation - The body s response to external injury and an attempt to heal tissues. Acute inflammation is helpful in limiting infections. Chronic inflammation can damage DNA and create a favorable environment for cancer growth. Insulin resistance - Condition in which the body produces insulin but cells cannot effectively respond to it. Insulin is a hormone necessary for cells to use blood sugar. If untreated, this condition can lead to Type 2 diabetes. Also associated with increased risk of some cancers. Invasion - The direct migration and penetration by cancer cells into neighboring tissues. Malignant - Harmful; describes a cancerous tumor

8 Metastasis - Process by which cancer breaks off from the initial site and spreads to other areas in the body. Mutation - Change in the genetic material (DNA) of the cell, which can be inherited or occur after birth. Phytochemicals - Biologically active compounds found in plant foods, which can prevent, delay or interrupt the cancer process in many ways. Tumor - Mass of tissue formed by a new growth of cells. Malignant tumors are called cancers and are caused by uncontrolled cell division. NEED MORE HELP? Visit for more information about diet, physical activity, weight and cancer prevention and survivorship. Or call to request additional brochures (up to three individual copies), such as: 10 Ways to Reduce Your Cancer Risk Eat Well for Life Move More for Life Reach Your Healthy Weight for Life The New American Plate These and other brochures with recipes can be downloaded for free at You can also visit the AICR Hotline online for answers to your questions about diet and cancer, or call Monday-Friday, 9 am-5 pm ET. A registered dietitian will return your call. Contact us at: American Institute for Cancer Research 1759 R Street, NW, P.O. Box Washington, DC or info@aicr.org 12 13

9 AICR Recommendations for Cancer Prevention 1. Be as lean as possible without becoming underweight. 2. Be physically active for at least 30 minutes every day. 3. Avoid sugary drinks. Limit consumption of energy-dense foods (particularly processed foods high in added sugar, or low in fiber, or high in fat). 4. Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans. 5. Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats. 6. If consumed at all, limit alcoholic drinks to two for men and one for women a day. 7. Limit consumption of salty foods and foods processed with salt (sodium). 8. Don t use supplements to protect against cancer. Special Population Recommendations 9. It is best for mothers to breastfeed exclusively for up to six months and then add other liquids and foods. Editorial Review Committee Elisa V. Bandera, MD, PhD, The Cancer Institute of New Jersey, UMDNJ-Robert Wood Johnson Medical School; Karen Collins, MS, RD, CDN, Nutrition Consultant; John Erdman, Jr., PhD, University of Illinois; Lidia Schapira, MD, Dana-Farber/Harvard Cancer Center; Amy L. Yaroch, PhD, Gretchen Swanson Center for Nutrition, University of Nebraska Medical Center; AICR executive staff. AICR is part of the World Cancer Research Fund global network, which consists of the following charitable organizations: the umbrella association, World Cancer Research Fund International (WCRF International); the American Institute for Cancer Research (AICR); World Cancer Research Fund (WCRF UK); World Cancer Research Fund Netherlands (WCRF NL); and World Cancer Research Fund Hong Kong (WCRF HK). You can support AICR s life-saving research and education efforts in a variety of ways: Make a donation online at Write to AICR, 1759 R Street, NW, P.O. Box 97167, Washington, DC ; or Include a bequest in your will. For more information, contact our Gift Planning Department at After treatment, cancer survivors should follow the recommendations for cancer prevention. And always remember do not smoke or chew tobacco. Copyright 2013 American Institute for Cancer Research 14 15

10 AICR Guidelines for Cancer Prevention The choices you make about food, physical activity and weight management can reduce your chances of developing cancer. Choose mostly plant foods, limit red meat and avoid processed meat. Be physically active every day in any way for 30 minutes or more. Aim to be a healthy weight throughout life. And always remember do not smoke or chew tobacco. About AICR The American Institute for Cancer Research (AICR) is the cancer charity that fosters cancer prevention and survivorship through healthy diets, physical activity and body weight. About one-third of the most common cancers could be prevented this way. By raising awareness of this message, we hope that many thousands of lives will be saved. The education and research programs of AICR are funded almost entirely by donations from the public. We fund cutting edge cancer research and help people make choices that reduce their changes of developing cancer. We are part of a global network of charities that are committed to preventing cancer.

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