Breast composition during and after puberty: the Chilean Growth and Obesity Cohort Study

Abstract

Background: Breast density (BD) is a strong risk factor for breast cancer. Little is known about how BD develops during puberty. Understanding BD trajectories during puberty and its determinants could be crucial for promoting preventive actions against breast cancer (BC) at early ages. The objective of this research is to characterize % fibroglandular volume (%FGV), absolute fibroglandular volume (AFGV), and breast volume (BV) at different breast Tanner stages until 4-year post menarche in a Latino cohort and to assess determinants of high %FGV and AFGV during puberty and in a fully mature breast.

Methods: This is a longitudinal follow-up of 509 girls from low-middle socioeconomic status of the Southeast area of Santiago, recruited at a mean age of 3.5 years. The inclusion criteria were singleton birth born, birthweight between 2500 and 4500 g with no medical or mental disorder. A trained dietitian measured weight and height since 3.5 years old and sexual maturation from 8 years old (breast Tanner stages and age at menarche onset). Using standardized methods, BD was measured using dual-energy X-ray absorptiometry (DXA) in various developmental periods (breast Tanner stage B1 until 4 years after menarche onset).

Results: In the 509 girls, we collected 1,442 breast DXA scans; the mean age at Tanner B4 was 11.3 years. %FGV increased across breast Tanner stages and peaked 250 days after menarche. AFGV and BV peaked 2 years after menarche onset. Girls in the highest quartiles of %FGV, AFGV, and BV at Tanner B4 and B5 before menarche onset had the highest values thereafter until 4 years after menarche onset. The most important determinants of %FGV and AFGV variability were BMI z-score (R² = 44%) and time since menarche (R² = 42%), respectively.

Conclusion: We characterize the breast development during puberty, a critical window of susceptibility. Although the onset of menarche is a key milestone for breast development, we observed that girls in the highest quartiles of %FGV and AFGV tracked in that group afterwards. Following these participants in adulthood would be of interest to understand the changes in breast composition during this period and its potential link with BC risk.

Keywords: Breast composition; Cohort study; Latino girls; Puberty.

Fig. 1

Description of breast composition and BMI z score in girls at different maturation ages. The Growth and Obesity Cohort Study (n=1,442 breast DXA scans). The figure represents the mean and standard deviation of breast composition components (%FGV, AFGV, and BV) and BMI at different time points of maturation: Tanner stage breast (B) B1, B2, B3, B4 before menarche onset, B4 after menarche onset, B5 before menarche onset, B5 after menarche onset, 1, 2 and 4 years after menarche onset. BV: breast volume; AFGV: absolute fibroglandular volume; %FGV: % of fibroglandular volume; BMI z-score: body mass index z-scores according to World Health Organization data 2007

Fig. 2

Distribution of Breast composition as function of days from onset of menarche and chronological age. The Growth and Obesity Cohort Study (n=1,442 breast DXA scans). %FGV: %fibroglandular volume; AFGV: absolute fibroglandular volume; BV: breast volume

Fig. 3

Distribution of breast composition (%FGV, AFGV, BV) and BMI across puberty. The Growth and Obesity Cohort Study (n=1,442 breast DXA scans). %FGV: %fibroglandular volumen; AFGV: absolute fibroglandular volume; BV: breast volume. a) data is stratified according to quartiles of %FGV at Tanner B4 or B5 before menarche onset, b) data is stratified according to quartiles of AFGV at Tanner B4 or B5 before menarche onset, c) data is stratified according to quartiles of BV at Tanner B4 or B5 before menarche onset, d) and e) data is stratified and followed according to quartiles of %FGV at Tanner B4 and B5 before menarche onset, f) data is stratified according to quartiles of BMI at Tanner B4 or B5 before menarche onset, g) h) and i) data is stratified according to quartiles of BV B4 or B5 before menarche onset