Abstract 4515: Epidemiological factors associated with breast density in Guam

Abstract Guam's breast cancer incidence is lower than the U.S. (86.6 vs. 126.8 per 100, 000), but mortality rates are higher (27.3 vs. 20.3). This disparity underscores the importance of improving screening and understanding risk factors. Breast density, categorized using the Breast Imaging Reporting and Data System (BIRADS), complicates tumor detection and correlates with malignancy risk. This study investigates the demographic and reproductive factors associated with breast density in Guam. Data from 1, 940 women undergoing mammography at FHP Health Center (Nov 2023-Aug 2024) in the HIPIMR study were analyzed. Associations between demographic factors (ethnicity, BMI) and reproductive factors (family history, age at menarche, menopausal status, parity, age at first live birth) with BIRADS categories were tested using chi-square tests. Reproductive factors were categorized by risk level. Multinomial logistic regression, adjusted for age and BMI, examined associations. Missing data (e.g., BMI, age, parity) were imputed using series means/medians. Women with extremely dense breast tissue (BIRADS D) were younger (mean age 57.13 vs. 58.32, p<0.001) and had lower BMI (74% vs. 37%, p<0.001). They more often experienced menarche after age 12 (58% vs. 51%, p=0.002), had fewer than two births (64% vs. 53%, p<0.001), and gave birth after age 30 (65% vs. 51%, p<0.001). Premenopausal (32%) and early menopause women (51%) had higher BIRADS D proportions (p<0.001, p=0.005). Regression showed BMI inversely associated with BIRADS D (OR = 0.815, 95% CI: 0.787-0.844), BIRADS C (OR = 0.875, 95% CI: 0.842-0.908), and BIRADS B (OR = 0.937, 95% CI: 0.907-0.968) (p<0.001). Family history increased odds of BIRADS D (OR = 1.64, 95% CI: 1.041-2.584, p=0.033) and BIRADS B (OR = 1.674, 95% CI: 1.042-2.69, p=0.033). Nulliparous women were 2.66 times more likely in BIRADS B (OR = 2.66, 95% CI: 1.157-6.114, p=0.021). Micronesians were less likely to belong to BIRADS D (OR = 0.419, 95% CI: 0.19-0.924, p=0.031) or BIRADS C (OR = 0.265, 95% CI: 0.092-0.766, p=0.014). BMI, parity, and childbirth age significantly influence breast density in Guam. Women with lower BMI, fewer births, or later childbirth were more likely to have extremely dense breast tissue, potentially complicating tumor detection. Ethnicity also played a role, with Micronesian women less likely in BIRADS D. While imputation mitigated missing data, bias remains possible. Future research should expand sample sizes and include malignancy risk via BIRADS outcomes for deeper insight. This research was funded by the National Cancer Institute: The University of Guam/University of Hawaii Cancer Center Partnership to Advance Cancer Health Equity (PIPCHE), Grant U54CA143728 (University of Guam, YCP)/Grant U54CA143727 (University of Hawaii Cancer Center). Citation Format: Gian M. Paras, Rodney S. Teria, Su Bin Jin, Grazyna Badowski, John Shepherd, Rose Grino. Epidemiological factors associated with breast density in Guam [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4515.