in the types of cancers studied may also affect the interpretability of the results. For example, studies of disease in which early detection through screening is a determinant of survival (such as breast cancer) may indicate that income level is a predictor of outcome because this measures the level of access to health care. Conversely, a cancer that is largely affected by lifestyle choices (such as colon cancer, which is associated with poor diet) may show a stronger relationship to education than to income.

Further complicating the issue is the fact that many members of ethnic minority groups are also among the most poor citizens of the population. This is more true in some regions of the country than others, as shown in Table 2-20.

Other Measures of Progress against Cancer

Beyond the measurement of cancer outcomes such as survival and mortality, efforts have been made to measure a number of attributes related to cancer, such as levels of screening for cancer and the incidence of risk factors for cancer such as smoking and diet, and to assess differences among members of ethnic minority groups and medically underserved individuals in these attributes. These measures are important in cancer prevention and control efforts.

Primary prevention measures related to behavioral risk factors have the greatest potential for reducing the incidence of and mortality from cancer in the United States. For example, smoking and diet have been shown to significantly influence the rate of death from cancer (estimated to cause 30 percent and 35 percent of deaths from cancer, respectively). Smoking is a well-established etiologic agent in lung cancer and has been associated with cancers of the cervix, stomach, pancreas, and colorectal system. High-fat, high-calorie, low-fiber diets often lead to obesity and have been associated with cancers of the breast, prostate, and digestive system. Excessive alcohol consumption increases the risk of cancers of the mouth and esophagus when combined with smoking, and has also been linked to breast and prostate cancers. Regular monitoring of the prevalence of these behavioral factors is an important tool in the national effort because it identifies segments of the population at high risk of developing cancer and permits the targeting of research and intervention efforts.

In addition to lifestyle changes, increasing levels of participation in cancer screening programs among high-risk groups can effectively reduce the burden of cancer. Early detection improves the rate of survival. For example, studies indicate that regular mammography can reduce the mortality rate from breast cancer by 35 percent among U.S. women ages 50 to 69 years (Harris et al., 1992). The introduction of the Pap smear in the 1940s effectively reduced the incidence of cervical cancer by 90 percent



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