Abstract
BackgroundTanner staging (TS), a five-stage classification indicating no breast tissue (TS1) to full breast development (TS5), is used both in health research and clinical care to assess the onset of breast development (TS2) and duration in each stage. Currently, TS is measured both visually and through palpation but non-invasive methods will improve comparisons across settings.MethodsWe used optical spectroscopy (OS) measures from 102 girls at the Ontario site of the LEGACY girls study (average age 12 years, range 10.0–15.4 years) to determine whether breast tissue optical properties map to each TS. We further examined whether these properties differed by age, body mass index (BMI), and breast cancer risk score (BCRS) by examining the major principal components (PC).ResultsAge and BMI increased linearly with increasing TS. Eight PCs explained 99.9% of the variation in OS data. Unlike the linear increase with age and BMI, OS components had distinct patterns by TS: the onset of breast development (TS1 to TS2) was marked by elevation of PC3 scores indicating an increase in adipose tissue and decrease in signal from the pectoral muscle; transition to TS3 was marked by elevation of PC6 and PC7 and decline of PC2 scores indicating an increase in glandular or dense tissue; and transition to TS4+ by decline of PC2 scores representing a further increase in glandular tissue relative to adipose tissue. Of the eight PCs, three component scores (PC4, PC5, and PC8) remained in the best-fitting model of BCRS, suggesting different levels of collagen in the breast tissue by BCRS.ConclusionsOur results suggest that serial measures of OS, a non-invasive assessment of breast tissue characteristics, can be used as an objective outcome that does not rely on visual inspection or palpation, for studying drivers of breast development.
Highlights
Tanner staging (TS), a five-stage classification indicating no breast tissue (TS1) to full breast development (TS5), is used both in health research and clinical care to assess the onset of breast development (TS2) and duration in each stage
We focus this paper on breast TS with TS1 referring to no breast development, TS2 as the first appearance of breast buds, TS3 where the areola and breast are larger than just buds but the areola does not stick out away from the breast, TS4 where the nipple is raised above the breast, and TS5 the mature breast
BMI body mass index, BCRS breast cancer risk score, principal components (PC) principal component, OS optical spectroscopy the linear increase with age and BMI, OS components had distinct patterns by TS: the onset of breast development (TS1 to TS2) was marked by elevation of PC3 scores; transition to TS3 was marked by elevation of PC6 and PC7 and decline of PC2 scores; and transition to TS4+ by the decline of PC2 scores
Summary
Tanner staging (TS), a five-stage classification indicating no breast tissue (TS1) to full breast development (TS5), is used both in health research and clinical care to assess the onset of breast development (TS2) and duration in each stage. Decline in the age of breast development [4] may account for some of the change. A long-established risk factor for breast cancer, has been relatively stable in recent decades [5]. As the interval between early breast development and the age at menarche (referred to as pubertal tempo) when the breast may be more susceptible to carcinogens has widened, it is essential to have other measures of pubertal development [6]. Age at breast development, age at menarche, and increased tempo were each independently associated with an increase in BC risk in a large prospective cohort study [7]. Compared with height and age at menarche, age at breast development has been more challenging to determine
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