Mammography screening methods and diagnostic results.

Mammograms from 12,636 women aged 40-54 years were examined by one screener first as one-view screening and later as two-view screening. With one-view screening, 542 (4.3%) women were recalled and 31 breast cancers were detected. With two-view screening, 349 (2.8%) women were recalled and 32 breast cancers were detected. Mammograms from 11,343 women aged 41-75 years were independently screened by 2 experienced screeners. A total of 76 breast cancers were diagnosed by 131 surgical biopsies. Both screeners detected 56 cancers. One screener detected 14 cancers alone, and the other detected 6 cancers alone. Thus, 15% more cancers were detected because of double reading. Five experienced screeners reviewed 120 sets of mammograms from the first screening round, including 74 women with breast cancer diagnosed in the first round or later. The mean increase in sensitivity by using two views, instead of one, was 2%. The median of the increase in cancer detection because of independent double reading was 14.5% with one-view screening and 12% with two-view screening. We invited 48,517 women aged 40-74 years to mammography screening. 86% participated, of which 4.8% were recalled for further examinations, and 1.0% were referred to surgery. A total of 241 (0.58%) breast cancers were diagnosed. Only 20% of the invasive cancers had lymph node metastasis and the median size was 16 mm. A total of 43,074 women aged 40-69 years were invited to screening. The attendance rate was 87% in the first screening round and 78% in the second screening. The recall rate was 4.6% and 5.7%, respectively. The breast cancer rate was 0.48% in both screening rounds. The rate of stage II or more advanced breast cancers decreased significantly from 0.16% in the first screening round to 0.08% in the second (p = 0.007).