A study of Black and Hispanic adolescent girls shows that even modest participation in organized sports is associated with favorable breast tissue composition and lower oxidative stress, highlighting adolescence as a critical window for cancer-related prevention research.
Study: Recreational physical activity and biomarkers of breast cancer risk in a cohort of adolescent girls. Image Credit: Svet foto / Shutterstock
In a recent study published in the journal Breast Cancer Research, researchers investigated the association between adolescent recreational physical activity (RPA) and biomarkers linked to breast cancer (BC) risk. The study focused on a cohort of 191 teenage girls from historically underrepresented backgrounds (Hispanic and Black/African American) and utilized optical spectroscopy and biomarker analysis to explore changes in breast tissue composition (BTC) and systemic stress.
Study findings revealed that girls who engaged in at least 2 hours of organized sports in the past week exhibited lower breast water content. This breast composition measure is positively correlated with, but not equivalent to, mammographic breast density and reduced oxidative stress, which may be relevant to future breast cancer risk. However, causal inference cannot be made.
Breast Cancer Risk and the Adolescent Window of Susceptibility
Breast cancer remains the most prevalent cancer subtype amongst women globally, with an estimated 2.3 million new cases diagnosed annually. Previous research has established that recreational physical activity (RPA) in adulthood reduces the risk of breast cancer by approximately 20%. However, the impact of physical activity during earlier life stages remains less understood.
A growing body of evidence indicates that adolescence represents a “window of susceptibility,” a period characterized by rapid mammary gland development during which the breast is particularly sensitive to external influences.
High mammographic breast density (the amount of fibroglandular tissue relative to fat) is now known to be a relatively accurate predictor of cancer risk in adults, yet little data exist on how modifiable behaviors (e.g., exercise, diet, and sleep) influence breast tissue composition measures that correlate with density during puberty. Furthermore, the biological pathways underlying these associations remain understudied.
Given that breast cancer incidence continues to rise, addressing this gap is vital, particularly for Black/African American and Hispanic populations, who are known to face higher risks of aggressive early-onset breast cancer and report lower levels of physical activity.
Study Design and Participant Characteristics
The present study aims to address these knowledge gaps and inform future public health recommendations by analyzing cross-sectional clinic-visit data from the Columbia Breast Cancer and the Environment Research Program (Columbia-BCERP), an American population-based urban cohort.
The study sample comprised 191 adolescent girls (ages 11–20), predominantly identifying as Hispanic (64%) or non-Hispanic Black/African American (36%). Breast tissue composition (BTC) was estimated using optical spectroscopy. This non-invasive technique uses red and near-infrared light to measure tissue chromophores, specifically quantifying water and collagen (linked to higher density) and lipids (linked to lower density).
Participants reported their past-week physical activity, which was self-reported, and was subsequently categorized as “organized” (e.g., sports teams, dance classes) or “unorganized” (e.g., playground play, biking).
Biomarker Assessment of Systemic Stress and Inflammation
Finally, participants’ biological samples (urine and blood) were analysed for systemic markers of stress and inflammation.
Oxidative stress, urine samples were tested for 15-F2t-isoprostane, a stable marker of lipid peroxidation (cell damage caused by free radicals).
Chronic inflammation, blood samples were analyzed for high-sensitivity C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α).
Unexpectedly, the study found no significant associations between RPA and systemic inflammatory markers (CRP, TNF-α, IL-6).
Associations Between Physical Activity and Breast Tissue Composition
Study analyses revealed that 51% of the girls reported no recreational physical activity in the past week, and 73% reported no participation in organized activities at all, highlighting a concerning prevalence of inactivity in these historically underrepresented populations.
However, for the minority who reported physical activity, the study revealed specific physiological associations.
Girls who participated in ≥2 hours of organized RPA in the past week had a significantly lower percent water content in their breast tissue than their inactive peers (β: -0.41, 95% CI: -0.77, -0.05). Notably, this association remained statistically significant even after adjusting for percent body fat, suggesting that these findings are not solely attributable to differences in adiposity. Lower percent water content is associated with lower mammographic breast density in adult populations, a factor linked to breast cancer risk.
Participation in ≥2 hours of organized sports was also associated with lower urinary concentrations of the oxidative stress marker 15-F2t-isoprostane (β: -0.50, 95% CI: -0.95, -0.05), indicating lower systemic oxidative stress.
Finally, the study revealed a relationship between biology and tissue structure; higher levels of oxidative stress were associated with greater collagen content in the breast (β = 0.15, 95% CI: 0.00, 0.31). While this finding suggests a potential link between oxidative stress and fibroglandular tissue composition, the authors note that causality cannot be inferred.
Importantly, the study did not observe associations between RPA and other breast tissue composition measures, including lipid content, collagen content, or optical index.
Interpretation and Public Health Implications
The present study suggests that organized physical activity during adolescence is associated with favorable breast tissue composition measures and lower oxidative stress, both of which are considered biomarkers linked to breast cancer risk. Because the analysis was cross-sectional and physical activity was assessed using self-reported past-week data, the findings cannot establish causation or long-term risk reduction.
Study analyses further indicate that structured (“organized”) sports were associated with these biomarkers, although the authors caution that differences between organized and unorganized activity may reflect measurement limitations, including imprecision in capturing activity intensity, rather than true biological differences.
These findings underscore the need for public health interventions that expand access to organized sports for adolescent girls. Future longitudinal studies are required to determine whether these biological associations persist into adulthood and translate into lower breast cancer incidence.
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