9781422280331

Cancer and Sickle Cell Disease

of cases is actually not very many. That means that around 90 percent of cancer cases are not inherited directly. So where do those come from? Although the vast majority cancers are not inherited in a direct way, you can inherit a greater risk for certain cancers. This is one reason doctors ask about your family medical history. Let’s say that your father had colon cancer. The colon is part of the digestive system, and it can develop malignant tumors that are hard to treat. We know that the risk for colon cancer can be inherited, so your doctor might recommend that you be checked for colon cancer sooner or more often than a person whose parents never had the disease. Inheriting a risk does not mean that you will definitely develop cancer, however. It just means that your chances may be higher. Family history is just one part of the picture. Genetic mutations that occur after a baby is conceived—meaning they did not come from the parents’ DNA but developed on their own—are called somatic changes, which simply means they were acquired. We all have somatic mutations, and they don’t always cause cancer. But the ones that do are sometimes caused by exposure to particular toxins, or carcinogens . The classic example is tobacco smoke, which contains many chemicals that are either suspected or proven cancer-causing agents. That’s why cigarette smoking can cause cancer not only in the person who smokes, but also in other people who are exposed to the smoke. Other known carcinogens include lead, which used to be added to gasoline and is still found in old paint; a material called asbestos, which used to be used in construction; and many forms of radiation, such as the machines that doctors use to perform X-rays. Lists of known and suspected carcinogens are kept by public health agencies such as the International Agency for Research on Cancer and the National Toxicology Program. It’s important to understand that a single exposure to a carcinogen is unlikely to cause cancer. Somatic mutations are not that straightforward. For instance, it’s considered safe to have an occasional X-ray, as long as the radiation levels are low and you don’t do it all the time. That’s why the technician who

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