American Medical Association Family Medical Guide - American Medical Association [19]
Cancer can originate anywhere in the body. Common sites include the lungs, breasts, lymph nodes, colon, bladder, and prostate gland. Cancer can spread through the body in two ways: Cancer cells from a tumor can invade neighboring tissues, and cancer cells from a tumor can penetrate blood vessels or lymphatic vessels, circulate through the bloodstream or lymphatic system, and invade healthy tissue in another part of the body.
What causes cancer?
Some people inherit genes that make them susceptible to developing particular types of cancer. Environmental factors that can trigger the changes in genes that lead to cancer include radiation, some chemicals, and some viruses and bacteria. For example, excessive exposure to radiation from sunlight has been linked to skin cancer. More than 60 different chemicals in cigarette smoke are known to cause cancer. The human papillomavirus, which causes the sexually transmitted disease genital warts, is responsible for most cases of cervical cancer in women, and the bacterium H. pylori causes many cases of stomach cancer.
Preventing Cancer
Many lifestyle factors can either raise or lower your risk of cancer. Although your genes also influence your susceptibility to developing cancer, genes are not necessarily destiny. Even if you have genes that could make you prone to cancer, the following measures can still help you reduce your risk and, at the same time, protect you from other common diseases:
• Don’t smoke or use other tobacco products. Cigarette smoking is the major cause of lung cancer and contributes to several other cancers, including cancer of the mouth, larynx, esophagus, stomach, pancreas, kidneys, and bladder. Use of smokeless tobacco has been linked to cancers of the mouth and throat.
• Eat a diet rich in vegetables, fruits, and whole grains. A number of substances such as antioxidants in plant foods (especially fruits, vegetables, and grains) have been found to interfere with the process that leads to cancer. Consuming foods that are low in fat (especially animal fat) may also help reduce cancer risk.
• Maintain a healthy weight. Being overweight increases the risk of some cancers, including cancers of the breast, uterus, and colon.
• Exercise regularly. Regular, vigorous exercise may reduce the risk of some cancers. Researchers don’t know exactly how physical activity prevents cancer but think that it may enhance the body’s immune system.
• Protect your skin from the sun. The risk of skin cancer, including melanoma (the most deadly type), can be greatly reduced by avoiding excessive sun exposure, wearing protective clothing in the sun, and using sunscreen.
• Drink alcohol only in moderation. Drinking excessive amounts of alcohol increases your risk of cancers of the mouth, throat, and esophagus—especially if you also smoke cigarettes. Together, alcohol and cigarettes make you 40 times more likely than nondrinking nonsmokers to develop these cancers.
• Engage in safer sex. The most common known cancer-causing virus in the US is the human papillomavirus (HPV), a sexually transmitted infection that causes cervical cancer in women.
• Have the recommended screening tests. Having regular cancer screening tests—such as a Pap smear (see page 140) to look for cervical cancer, and a colonoscopy (see page 767) to look for colon cancer—can detect potential problems early, when they are generally easier to treat and the chances for a cure are better.
When cancer spreads
If cancer cells enter blood vessels, they can be carried through the bloodstream to other parts of the body and invade healthy tissues there. The spread of cancer from one area of the body to another is called metastasis.
Most Common Cancers
Although more people have breast cancer or prostate cancer than lung