Positive predictive value of screening mammography by age and family history of breast cancer

Mammography appears to be most effective in detecting breast cancer in women 50 years or older or in women 40 years or older with a family history of breast cancer. A total of 31,814 women 30 years old or older had mammograms during a seven-year period. The number of breast cancers detected for each abnormal examination increased with the age of the women. Women aged 50 years and older accounted for 38.3% of all women screened, yet 74% of all breast cancers were found in these women. In the group of women 50 years and older without a family history of breast cancer, 10 cancers were detected for each 1,000 exams. For women younger than 50, the number dropped to two cancers for each 1,000 exams. Nine cancers were detected for each 1,000 exams of women between the ages of 40 and 49 with a family history of breast cancer. For women aged 50 to 59 years with a family history of breast cancer, the number rose to 26 cancers detected in every 1,000 exams.
Objective. - To determine the positive predictive value (PPV) of low-cost screening mammography according to age and family history of breast cancer. Design. - Cross-sectional. Setting. - Six counties in northern California. Participants. - A total of 31 814 women aged 30 years and older referred for mammography to the University of California, San Francisco, Mobile Mammography Screening Program from April 18, 1985, through November 20, 1992. Measurements. - Breast cancer risk profile, two standard mammographic views per breast, and follow-up of abnormal screening examinations. Results. - Although women aged 50 years or older constituted only 38.3% of all women who received first-screening mammography, 74% of breast cancers were detected in this group. Ten cancers were diagnosed per 1000 first-screening examinations in women aged 50 years or older, with 14.8 diagnostic procedures per cancer diagnosed compared with two cancers per 1000 screening examinations and 48.3 diagnostic tests per cancer diagnosed in women younger than 50 years. The PPV of first-screening mammography (number of breast cancers detected per abnormal examination) increased with age: .03 for those aged 30 to 39 years; .04 for those aged 40; .09 for those aged 50 to 59; .17 for those aged 60 to 69; and .19 for those aged 70 years or older ([chi.sup.2] for trend, P