Wasson et al., 1993]), the question of which cancers should be treated after detection with PSA testing is critical

The absence of proof that screening can reduce mortality from prostate cancer, together with the strong potential that screening will increase treatment-related morbidity, argue against a policy of routine screening in asymptomatic men. Thus, the U.S. Preventive Services Task Force (1996) does not recommend routine screening for prostate cancer. However, the American Cancer Society does recommend yearly PSA testing beginning at age 50 for white men and at age 40 for African American men, in whom risk of the disease is higher.

Breast Cancer Screening

Each year, some 180,000 women are diagnosed with breast cancer in the United States (NCHS, 1998b). This accounts for about 30% of all incident cancers among women. Each year, 44,000 women die of breast cancer (NCHS, 1998b), making it the second-leading cause of cancer deaths among American women, after lung cancer. Breast cancer is extremely rare among women younger than 20, and is uncommon among women under the age of 30. Incidence rates increase sharply with age, however, and become substantial before age 50 years. Rates continue to rise, although less quickly, in postmenopausal women.

As reviewed by the U.S. Preventive Services Task Force (1996), several clinical trials conducted among women aged 40 years and older have shown an overall reduction of breast cancer mortality due to screening. The average reduction is 20–30% (over roughly a 10-year period) for women aged 50–69 who are screened periodically for breast cancer (U.S. Preventive Services Task Force, 1996). However, there is no consensus about the optimal screening interval for women in this age group. Although annual screening has been recommended by many groups, an analysis of data from Sweden revealed little evidence that screening every year provides a greater benefit than does screening every 2 years (Tabar et al., 1987).

Based on data from clinical trials, there is disagreement in the scientific community over whether routine mammographic screening should be recommended for women in their forties. This disagreement has at times been strident and strong (Taubes, 1997). Although none of the randomized clinical trials enrolled enough women in their forties to study the benefit of screening in this age group with statistical confidence, a sum-

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