Cancer is second only to heart disease as the leading cause of death in the United States. One-half of all men and one-third of all women will develop cancer at some time in their lives. Although prostate cancer is the most common form of cancer in males, and breast cancer is the most common form in females, lung cancer causes the highest mortality rates for either gender (American Cancer Society, 2007). African-Americans have lower survival rates for most cancers compared with other groups of people. This may be due to a variety of factors, including limited access to health care, little or no medical insurance, lack of a primary health care provider, homelessness, poverty, lack of knowledge on early diagnosis and treatment, and greater exposure to carcinogens (McCance & Roberts, 1998).

The five-year survival rate from all cancers is currently estimated at 58% (American Cancer Society, 2000). Generally, if there is no detectable recurrence of cancer for five years following the initial diagnosis, a person is considered to be in remission or cured. However, many people considered cured continue to demonstrate limitations or disabilities from their cancer or its treatment. These disabilities include movement dysfunctions, limited physical activity levels, chronic fatigue, and depression. These limitations and disabilities can be improved through rehabilitation and physical training (Gerber & Augustine, 2000, Pinto & Maruyama, 1999, Dimeo, et al., 1998, Segar, et al., 1998, Dimeo, et al., 1997, Friendenreich & Courneya, 1996).

Cancer is primarily caused by environmental factors and lifestyle practices (Lichtenstein, et al., 2000). This phenomenon was originally observed when people from countries with low cancer rates migrated to countries with high cancer rates. As migrating people began to adopt the customs of their new land and to be exposed to new environmental conditions, they would subsequently begin to develop cancers at a rate and type similar to that of their new country or geographical area. This increase in cancer rates was seen in the increases in breast and colon cancer rates in people from Japan who moved first to Hawaii and then to California (McCance & Roberts, 1998, Fraumeni, 1982). Colon cancer and breast cancer are relatively rare in Japan, but as the Japanese became gradually more westernized in their customs and environmental conditions, their cancer rates became similar to those in the United States. Increases in the incidence rates for colon cancer following migration appear to take two or three decades, while increases in breast cancer rates require more than one generation (Fraumeni, 1982).

Variations can also be seen in cancer rates in different geographical locations within the same country. Mapping of mortality rates for different types of cancers within the United States has shown that certain cancers occur more frequently in particular geographical regions and that this phenomenon appears to be related to environmental exposures (Atlas of Cancer Mortality in the United States, United States Department of Health and Human Services, 2000). Examples of geographically influenced cancers include the high rates of colon cancer in the northeast quadrant of the United States compared with the rest of the country, and the higher rates of ovarian cancer in the northern states compared to the southern states.

Upward trends in some cancers over time may reflect changes that have occurred in lifestyles, medical practices, and environmental factors. Smoking is a lifestyle change that dramatically reflects the upward trend seen in lung cancer rates during the last 50 years (Zeegers, et al., 1989). Changes in medical practices that reflect upward trends in cancer rates include the use of menopausal estrogens and increases seen in endometrial, ovarian, and breast cancers, as well as the use of head and neck X-rays during childhood that are reflected in increases in thyroid cancers (McCance & Roberts, 1998, Fraumeni, 1982). Environmental factors that appear to increase cancer rates include radon gas exposures, industrial emissions such as arsenic or benzene, and ultraviolet exposures from thinning ozone layers (McCance & Roberts, 1998; Fraumeni, 1982).

Compared with environmental and lifestyle factors, genetic influences contribute only a small percentage to cancer rates (Lichtenstein, et al., 2000). Inherited cancers tend to occur earlier in life and typically cause multiple growths in the same organ (Fraumeni, 1982). Although some cancers appear to follow racial and ethnic lines, it is difficult to separate genetic influences from environmental and lifestyle factors as the cause of a cancer. Examples of cancers that appear to follow racial and ethnic lines include nasopharyngeal cancers in the Chinese, gallbladder cancer in American Indians and some Hispanic groups, and skin cancers in ethnic groups that lack protective skin pigmentation (McCance & Roberts, 1998, Fraumeni, 1982).

Some families are prone to developing certain types of cancers, but the incidence of family-related cancers is very low. For example, familial breast cancer accounts for only 5% of all breast cancers (McCance & Roberts, 1998). Other types of familial cancers include prostate, stomach, lung, and colon cancer. Even though these cancers tend to occur more often in certain families, not every individual from a "susceptible family" will develop these cancers. Researchers believe that the risk for developing cancer is more related to an individual's environment and lifestyle than to familial tendencies (Chlebowski, 2000, McCance & Roberts, 1998). A recent study by Lichtenstein and colleagues (2000) demonstrated this phenomenon. These researchers found that an individual's environment and lifestyle played a greater role in determining whether a person would develop cancer than their familial risk. These investigators examined cancer rates among 44,788 sets of twins. They did find an increased number of prostate, colorectal and breast cancer rates among the twins of an affected twin. However, statistical modeling demonstrated that environmental and lifestyle practices had a far greater impact on determining whether the unaffected twin would, in fact, develop these familial cancers. Therefore, even when there is increased family susceptibility for certain cancers, persons can modify their risk for developing cancer by changing their environment or lifestyle practices.