BREAST-CANCER AND EARLIER DETECTION EFFORTS - REALIZED AND UNREALIZEDIMPACT ON STAGE

Objective.-To test our hypotheses that increased public and profession al education in breast cancer detection (screening mammography, clinic al breast examination, and breast self-examination) would lead to dete ction at earlier stages of disease with each of the three methods. Des ign and Setting.-A survey study of all pathologically diagnosed breast cancers in a defined geographic area (all nonfederal general hospital s in the state of Vermont) before (1975-1984, n=1652) and after (1989- 1990, n=683) screening mammography became more commonly used. Main Out come Measures.-Method of detection of breast cancer and stage at detec tion. Results.-The age-adjusted annual incidence rate of breast cancer among adult women was 99 per 1 00 000 during the years 1975 to 1984 c ompared with 169 per 1 00 000 during 1989-1990 (P<.001). Mammography a s the method of detection increased in use from 2% to 36% (P<.001). In the later era, invasive breast cancers were detected at more favorabl e TNM stage (P<.001); mean maximum tumor diameter was smaller (2.2 cm vs 2.7 cm; P<.001); percentage of histologically positive nodes was lo wer (37% vs 47%; P<.001). When mammographically detected cancers were excluded from the analysis of invasive cancers, the mean maximum tumor diameter and percentage of negative nodes in the two eras were simila r even though there was an apparent shift to detection at an earlier c linical stage. Conclusion.-The earlier stages of detection and the sud den increase in incidence could almost entirely be credited to screeni ng mammography. Mammographic screening had a much greater impact on st age at detection in women aged 50 years and older than in those younge r than 50 years.