A PROSPECTIVE-STUDY OF THE VALUE OF MAMMOGRAPHIC PATTERNS AS INDICATORS OF BREAST-CANCER RISK IN A SCREENING EXPERIENCE

The association between mammographic parenchymal patterns and the risk of subsequent breast cancer was studied in a cohort of 17 911 women a ged 40-70 years, enrolled in a mammographic screening program. The coh ort was prospectively followed-up for 5 years after blind attribution of mammographic pattern. Incident cancers, either screen- or interval- detected, were monitored through the screening program and by the loca l cancer registry. Multivariate analysis adjusting for the confounding effect of age, demonstrated an independent and significant associatio n between mammograpic patterns and breast cancer risk. The relative ri sk of subsequent breast cancer, assumed to be 1 for N1 pattern, was 2. 39 (1.0-5.7) for P1, 4.02 (1.7-9.3) for P2, and 5.01 (1.9-13.3) for DY category, respectively. The relative risk of P2-DY with respect to N1 -P1 categories was 2.09 (1.4-3.1). A diagnostic delay, possibly due to the 'masking effect' of a radiologically dense breast, was evident fo r P2-DY with respect to N1-P1 cancers (proportion of Stage I cancers = 42% vs. 69%). These results suggest the adoption of a shorter rescree ning interval in P2-DY subjects.