Kayla R. Getz

Supplemental Figure 1: Flowchart displaying how we arrived at the final analytic sample. Among the women recruited to the study, 127 were missing breastfeeding duration and 32 were missing values for all of the MBD measures. An additional 18 participants were missing values for one of the confounding variables; 11 women were missing age at menarche, 1 woman was missing BMI and 6 women were missing information about family history of breast cancer.

Supplemental Table 1 shows results from IPW analysis.

Supplemental Figure 1: Flowchart displaying how we arrived at the final analytic sample. Among the women recruited to the study, 127 were missing breastfeeding duration and 32 were missing values for all of the MBD measures. An additional 18 participants were missing values for one of the confounding variables; 11 women were missing age at menarche, 1 woman was missing BMI and 6 women were missing information about family history of breast cancer.

Breastfeeding is inversely associated with breast cancer risk but the associations of breastfeeding with mammographic breast density (MBD) are not clear. We investigated the association between breastfeeding and volumetric measures of MBD (volumetric percent density (VPD), dense volume (DV) and non-dense volume (NDV)) and evaluated whether it differs by race, menopausal status, and body mass index (BMI). The study population was comprised of 964 women (67% non-Hispanic white, 29% non-Hispanic black) who had screening mammography at Washington University School of Medicine, St. Louis, MO. VPD, DV and NDV were log10 transformed. We performed multivariable linear regression models adjusted for age, BMI, family history of breast cancer, race, and age at menarche among all participants and exclusively in parous women. Mean age was 50.7 years. VPD was 12% lower among women who breastfed 0-6 months, (10^β=0.88, 95%CI (0.79,0.98)) compared to nulliparous women. Breastfeeding was inversely associated with DV (parous never breastfed: 10^β=0.93, 95%CI (0.83,1.04), breastfed 0-6 months: 10^β=0.91, 95%CI (0.79,1.05), breastfed 7-12 months: 10^β=0.94, 95%CI (0.81,1.10), breastfed >12 months: 10^β=0.87, 95%CI (0.78,0.98), p-trend=0.03). BMI modified the association between breastfeeding and VPD. Women who breastfed for 0-6 months and had a BMI < 25kg/m2 had lower VPD compared to nulliparous women, but among women with a BMI ≥ 25kg/m2 there was no association (p-interaction=0.04). In this diverse study population, the association of breastfeeding with VPD appears to be modified by BMI, but not by race or menopausal status. Future research exploring the associations of breastfeeding with other mammographic features are needed.

Supplemental Figure 1: Flowchart displaying how we arrived at the final analytic sample. Among the women recruited to the study, 127 were missing breastfeeding duration and 32 were missing values for all of the MBD measures. An additional 18 participants were missing values for one of the confounding variables; 11 women were missing age at menarche, 1 woman was missing BMI and 6 women were missing information about family history of breast cancer.

Supplemental Table 1 shows results from IPW analysis.

Supplemental Table 1 shows results from IPW analysis.

Background: Studies investigating the associations of self-reported aspirin use and mammographic breast density (MBD) have reported conflicting results. Therefore, we investigated the associations of aspirin metabolites with MBD in premenopausal women. Methods: We performed this study on 705 premenopausal women who had a fasting blood draw for metabolomic profiling. We performed covariate-adjusted linear regression models to calculate the least square means of volumetric measures of MBD [volumetric percent density (VPD), dense volume (DV), and nondense volume (NDV)] by quartiles of aspirin metabolites [salicyluric glucuronide, 2-hydroxyhippurate (salicylurate), salicylate, and 2,6-dihydroxybenzoic acid]. Results: Approximately 13% of participants reported taking aspirin in the past 12 months. Aspirin users had higher levels of 2-hydroxyhippurate (salicylurate), salicylate, and salicyluric glucuronide (peak area) than nonusers, but only the mean peak area of salicyluric glucuronide was increased by both dose (1–2 tablets per day = 1,140,663.7 and ≥3 tablets per day = 1,380,476.0) and frequency (days per week: 1 day = 888,129.3, 2–3 days = 1,199,897.9, and ≥4 days = 1,654,637.0). Aspirin metabolites were not monotonically associated with VPD, DV, or NDV. Conclusions: Given the null results, additional research investigating the associations of aspirin metabolites in breast tissue and MBD is necessary. Impact: Elucidating the determinants of MBD, a strong risk factor for breast cancer, can play an important role in breast cancer prevention. Future studies should determine the associations of nonaspirin NSAID metabolites with MBD.

Breastfeeding is inversely associated with breast cancer risk but the associations of breastfeeding with mammographic breast density (MBD) are not clear. We investigated the association between breastfeeding and volumetric measures of MBD [volumetric percent density (VPD), dense volume (DV), and non-dense volume (NDV)] and evaluated whether it differs by race, menopausal status, and body mass index (BMI). The study population was comprised of 964 women (67% non-Hispanic White, 29% non-Hispanic Black) who had screening mammography at Washington University School of Medicine, St. Louis, MO. VPD, DV and NDV were log10 transformed. We performed multivariable linear regression models adjusted for age, BMI, family history of breast cancer, race, and age at menarche among all participants and exclusively in parous women. Mean age was 50.7 years. VPD was 12% lower among women who breastfed 0–6 months, [10β = 0.88, 95% confidence interval (CI; 0.79–0.98)] compared with nulliparous women. Breastfeeding was not associated with VPD among women who breastfed >7 months. Breastfeeding was inversely associated with DV [parous never breastfed: 10β = 0.93; 95% CI (0.83–1.04), breastfed 0–6 months: 10β = 0.91, 95% CI (0.79–1.05), breastfed 7–12 months: 10β = 0.94; 95% CI (0.81–1.10), breastfed >12 months: 10β = 0.87, 95% CI (0.78–0.98), Ptrend = 0.03]. BMI modified the association between breastfeeding and VPD. Women who breastfed for 0–6 months and had a BMI < 25 kg/m2 had lower VPD compared with nulliparous women, but among women with a BMI ≥ 25 kg/m2 there was no association (Pinteraction = 0.04). In this diverse study population, the association of breastfeeding with VPD appears to be modified by BMI, but not by race or menopausal status. Future research exploring the associations of breastfeeding with other mammographic features are needed.Prevention Relevance:Breastfeeding for up to 6 months may be associated with lower VPD among women with a BMI < 25 kg/m2. The potential role of MBD in mediating the associations of breastfeeding with breast cancer risk in a select group of women deserves further evaluation.See related Spotlight, p. 309

Supplemental Table 1 shows results from IPW analysis.