The original attending radiologists had a false-negative rate of 21% (115 of [427 + 115]). CAD prompting could have potentially helped reduce this false-negative rate by 77% (89 of 115) without an increase in the recall rate.

Standardized abnormal interpretation ratios and standardized cancer detection ratios provide a method of comparing two important performance measures in a screening program. A minimum of 2,500 interpretations per year is associated with lower abnormal interpretation rates and average or better cancer detection rates.

Spiculated masses and architectural distortions are the predominant appearances of invasive lobular carcinoma, and a computer-aided detection system correctly marked a high percentage of invasive lobular carcinoma lesions.

Breast cancer screening programs have been initiated in many countries in the past decade. To determine the impact of the Screening Mammography Program of British Columbia (SMPBC), disease and treatment outcomes for women with breast cancer diagnosed in BC between 1989 and 1996 were compared on the basis of attendance at the SMPBC. An SMPBC attender was a women diagnosed with breast cancer within three years of an SMPBC screen, regardless whether the cancer was detected as a result of that screen. Of the 13,636 women aged 40-89 years diagnosed with breast cancer in BC during the study period, 2,647 (19.4%) were SMPBC attenders. 73.5% of SMPBC attenders (N = 1,946) and 74.2% of non-attenders (N = 8,149) were referred to the BC Cancer Agency and had pathology, staging, treatment, and outcome information available. SMPBC attenders compared with non-attenders were more likely to have in situ disease alone, and those with invasive cancers had smaller tumors which were less likely to have grade III histology and less likely to have spread to axillary lymph nodes (all P < 0.001). SMPBC attenders were more likely to be treated with breast conservation and less likely to receive adjuvant chemotherapy or tamoxifen (P < 0.001). Log-rank tests showed local (P = 0.017), distant (P < 0.001), and overall (P < 0.001) disease-free survival were better for SMPBC attenders. These favorable surrogate endpoints suggest that the benefits of breast screening as demonstrated by randomized trials can be translated into community practice by an organized breast screening program.

Results-895 849 screening mammographies were provided to 335 433 women. 51.3% of women were age 50-69 years. Abnormalities were identified on 57 454 screens (6.4%) from which 3304 cancers were detected. Abnormal call rates were higher on first (9.8%), compared with subsequent screens (4.4%) and declined with age: 7.7% at age < 40 to 5.4% for age 70-79 years. Cancer detection rates were higher on first (5.0 per 1000) compared with subsequent screens (2.8 per 1000) and increased smoothly with age from 1.4 to 8.2 per 1000 from age < 40 to age 80 years and older. Twenty per cent of cancers were non-invasive. The median size of invasive cancers was 14 mm and 81% had no axillary lymph node metastases. The 12 month interval cancer rate was 0.6 per 1000 and did not vary significantly with age or screening history. The prevalence to expected incidence ratio was 3.1 for women age 50-79 years. Conclusion-Across a broad range of ages, surrogate indices of screening mammography success have been achieved in a population based, North American, organised breast cancer screening programme. (J Med Screen 2000;7:152-159)