Cancer is a group of more than 100 different diseases, each with its own unique set of risk factors. Risk factors are elements that increase the possibility of developing a specific disease or condition. Over a lifetime, it is estimated that one in three people will develop cancer, according to the National Cancer Institute (NCI).

Cancer develops as a result of an uncontrolled growth of cells. In normal cell function, cells divide and die in an organized fashion. As cells grow old, they die, allowing for new cells to take their place. When old cells do not die and the body continues to create new cells, they collect to form a tumor.  A tumor can be either benign (noncancerous) or malignant (cancerous).

There is more than one risk factor for most cancers. Some risk factors can be controlled, such as lifestyle habits. These factors can include smoking, alcohol use, diet and exercise. Other risk factors cannot be controlled by an individual, such as age, race, sex and genetic factors.

Although risk factors may be divided into controllable and uncontrollable categories, such distinctions may be counterproductive. In many cases, an environmental risk factor may combine with a genetic predisposition and create an opportunity for cancer to develop. Researchers believe that the development of cancer often involves environmental factors that directly or indirectly alter cells. These experts contend that nearly all cancers occur as a result of a combination of factors and it is nearly impossible to determine a single cause. Controllable and uncontrollable factors can combine to a point where identifying one or the other as the exact cause is extremely difficult. 

The division of risk factors into categories may serve to provide better awareness for both patients and medical professionals. Awareness of controllable risk factors can help patients avoid them by quitting smoking, maintaining a healthy weight and protecting their skin from sun exposure. Awareness of both controllable and uncontrollable risk factors in a patient’s medical history provides physicians with valuable information to schedule screening tests and make diagnoses.

Many risk factors have been identified by scientists conducting epidemiological studies that analyze both environmental and genetic risk factors. According to the American Cancer Society, about 75 to 80 percent of cancers can be attributed to environmental factors, including tobacco use, diet, infectious agents and occupational exposure.

Much of this information has come from studying people who migrate from an area of high cancer risk to an area of low cancer risk (or vice versa). These migrant studies demonstrate that these people soon take on the cancer rates of their new area. Because genetic changes take several generations, it suggests that the cancer attack rates may be related to environmental causes.