Abstract A130: Effect of high-dose estrogen exposure in adolescence on mammographic density in adulthood.

Since adolescence is an important stage of mammary development, exposure to high-dose estrogens at this time may have long-term effects on breast tissue and therefore mammographic density. It is well-established that women with greater mammographic density for age and BMI are at an increased risk of breast cancer.

We conducted a retrospective cohort study of women from the Australian Tall Girls Study who were 40 years or older and had been assessed for tall stature during adolescence between 1959 and 1993. Eligible women included 263 who had been treated during adolescence with high-dose estrogens and 254 who had not been treated. Treated women had received one of two types of estrogen: 3mg diethylstilbestrol (DES) daily, or 150 μg ethinyl estradiol (EE).

A mammogram within the previous two years was obtained from 167 treated women (mean age 48.4 yrs) and 142 untreated women (mean age 46.2 yrs). The total area of the breast image and the area of mammographically dense tissue (dense area), and hence non-dense area and percent mammographic density (PMD), were calculated from digitally scanned cranio-caudal mammographic films using a computer thresholding technique. Reproductive history, lifestyle factors, hormone exposure, treatment and anthropometric data were collected from medical records and by telephone interview using a structured questionnaire.

After adjusting for age and BMI, treated women had, on average, 17% lower dense area (p=0.03); adjusted means for treated and untreated women were 24.5 cm² (95% CI: 21.8, 27.2) and 29.1 cm² (95% CI: 26.0, 32.4), respectively. There was no difference in adjusted means between treated and untreated women for non-dense area [71.7 cm² (95% CI: 66.2, 77.7) versus 70.5 cm² (64.7, 76.9); p=0.78], PMD [ 24.8 % (95% CI: 22.4, 27.4) versus 27.7% (95% CI: 24.8, 30.7); p=0.16], or total area [105.6 cm² (95%CI: 100.1,111.4) vs 109.3 cm² (95%CI: 103.1,115.8); p=0.41].

High-dose estrogen treatment for tall stature in adolescence is unlikely to increase risk of breast cancer through mechanisms related to mammographic density.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):A130.