FAVORABLE CHANGE IN MAMMOGRAPHIC PARENCHYMAL PATTERNS AND BREAST-CANCER RISK-FACTORS

The aim of our study was to estimate the incidence of favorable mammog raphic patterns and to assess the incidence by risk factors of breast cancer. Data relate to 1,947 women aged 40-47 years who were screened by mammography every second year and whose mammographic parenchymal pa ttern at initial screening was either P2 or DY (Wolfe's classification ). The pattern was assessed at each screening round. The incidence of NI,PI parenchymal pattern by risk factors was estimated. The Cox propo rtional hazards model was applied in univariate and multivariate analy ses of the data. The incidence of NI,PI pattern was 12.5/100 woman yea rs among women with P2,DY pattern at the beginning of follow-up. The r elative risk of NI,PI pattern adjusted for th eother risk factors for women aged 45 years or more was 1.7 [95% confidence interval (CI) 1.5- 1.9] compared with younger women. The adjusted relative risk of NI,PI pattern among women with a body mass index (BMI) of 25 or more was 2.1 (95% CI 1.6-2.8) compared with women with a BMI of less than 20; wome n with more than 2 pregnancies had a 30% higher adjusted relative risk (RR = 1.3, 95% CI 1.1-1.6) than women with no pregnancies. The incide nce of favorable mammographic parenchymal pattern was significantly re lated to old age, large BMI and multiparity. The effects of age and BM I on incidences of favorable and unfavorable change potentiate each ot her but not that of parity. (C) 1998 Wiley-Liss, Inc.