There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start – for example, cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma.
Cancer types can be grouped into broader categories:
- 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.
- Leukemia: Cancer that starts in blood-forming 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.
All cancers begin in cells. To understand cancer, it’s helpful to know what happens when normal cells become cancer cells. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should, and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumor.
Not all tumors are cancerous; tumors can be benign or malignant. Benign tumors aren’t cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Malignant tumors are cancerous.
Cells in these tumors can invade nearby tissues and spread to other parts of the body. Some cancers do not form tumors. For example, leukemia is a cancer of the bone marrow and blood.
What are the risk factors for cancer?
1. Growing older
The most important risk factor for cancer is growing older. Most cancers occur in people over the age of 65. But people of all ages, including children, can get cancer, too.
Tobacco use is the most preventable cause of death. Using tobacco products or regularly being around tobacco smoke (environmental or secondhand smoke) increases the risk of cancer of the lung, larynx (voice box), mouth, esophagus, bladder, kidney, throat, stomach, pancreas, or cervix. Smokers are also more likely to develop acute myeloid leukemia (cancer that starts in blood cells). People who use tobacco (snuff or chewing tobacco) are at an increased risk of cancer of the mouth. Quitting is important for anyone who uses tobacco, even people who have used it for many years.
Having more than two drinks each day for many years may increase the chance of developing cancers of the mouth, throat, esophagus, larynx, liver, and breast. The risk increases with the amount of alcohol that a person drinks. For most of these cancers, the risk is higher for a drinker who uses tobacco. Drinking in moderation means no more than one drink per day for women and no more than two drinks per day for men.
4. Poor diet, lack of physical activity, or being overweight
Studies suggest that people whose diet is high in fat have an increased risk of cancers of the colon, uterus and prostate. Lack of physical activity and being overweight are risk factors for cancers of the breast, colon, esophagus, kidney, and uterus.
Having a healthy diet, being physically active, and maintaining a healthy weight may help reduce cancer risk. A healthy diet includes food less in fat content and high in fiber, vitamins, and minerals like whole-grain breads and cereals and 5 to 9 servings of fruits and vegetables every day. Moderate physical activity (such as brisk walking) for at least 30 minutes on 5 or more days each week can check your weight.
5. Family history of cancer
Some gene changes that increase the risk of cancer are passed from parent to child. These changes are present at birth in all cells of the body. It is uncommon for cancer to run in a family. However, certain types of cancer do occur more often in some families than in the rest of the population. For example, cancers of the breast, ovary, prostate, and colon sometimes run in families. Most of the time, multiple cases of cancer in a family are just a matter of chance.
If you think you may have a pattern of a certain type of cancer in your family, you may want to talk to your doctor. Your doctor may suggest exams that can detect cancer early. You may want to ask your doctor about genetic testing.
These tests can check for certain inherited gene changes that increase the chance of developing cancer. But inheriting a gene change does not mean that you will definitely develop cancer. It means that you have an increased chance of developing the disease.
6. Certain chemicals and other substances
People who have certain jobs (such as painters, construction workers, and those in the chemical industry) have an increased risk of cancer. Many studies have shown that exposure to asbestos, benzene, benzidine, cadmium, nickel, or vinyl chloride in the workplace can cause cancer.
Follow instructions and safety tips to avoid or reduce contact with harmful substances both at work and at home. Although the risk is highest for workers with years of exposure, it makes sense to be careful at home when handling pesticides, used engine oil, paint, solvents, and other chemicals.
It causes early aging of the skin and skin damage that can lead to skin cancer. It is best to avoid the midday sun (from mid-morning to late afternoon) whenever possible. You also should protect yourself from UV radiation reflected by sand, water, snow, and ice. UV radiation can penetrate light clothing, windshields, and windows. Wear long sleeves, long pants, a hat with a wide brim, and sunglasses with lenses that absorb UV. Sunscreen may help prevent skin cancer, especially sunscreen with a sun protection factor (SPF) of at least 15. But sunscreens cannot replace avoiding the sun and wearing clothing to protect the skin.
8. Ionizing radiation
Radioactive fallout can come from accidents at nuclear power plants or from the production, testing, or use of atomic weapons. People exposed to fallout may have an increased risk of cancer, especially leukemia and cancers of the thyroid breast, lung, and stomach. Medical procedures like X-rays and radiation therapy (used to treat cancer) also can cause cancer. The risk of cancer from low-dose x-rays is extremely small, while from radiation therapy it is slightly higher. For both, the benefit nearly always outweighs the small risk.
9. Some viruses and bacteria
Being infected with certain viruses or bacteria may increase the risk of developing cancer:
a) Human Papilloma Viruses (HPVs): HPV infection is the main cause of cervical cancer. It also may be a risk factor for other types of cancer.
b) Hepatitis B and Hepatitis C viruses: Liver cancer can develop after many years of infection with hepatitis B or hepatitis C.
c) Human T cell leukemia/ lymphoma virus (HTLV-1): Infection with HTLV-1 increases a person’s risk of lymphoma and leukemia.
d) Human Immunodeficiency Virus (HIV): HIV is the virus that causes AIDS. People who have HIV infection are at greater risk of cancer, such as lymphoma and a rare cancer called Kaposi’s Sarcoma.
e) Epstein-Barr Virus (EBV): Infection with EBV has been linked to an increased risk of lymphoma.
f) Helicobacter pylori: This bacterium can cause stomach ulcers. It also can cause stomach cancer and lymphoma in the stomach lining.
Do not have unprotected sex or share needles. You can get an HPV infection by having sex with someone who is infected. You can get hepatitis B, hepatitis C, or HIV infection from having unprotected sex or sharing needles with someone who is infected. You may want to consider getting the vaccine that prevents hepatitis B infection.
10. Certain hormones
Doctors may recommend hormones (estrogen alone or estrogen along with progestin) to help control problems (such as hot flashes, vaginal dryness, and thinning bones) that may occur during menopause. However, studies show that menopause hormone therapy can cause serious side effects. Hormones may increase the risk of breast cancer, heart attack, stroke, etc.
Dr Vijay Anand P Reddy is Director of Apollo Cancer Hospital, Hyderabad.