Distribution Of Mammographic Density And Its Influential Factors Among Chinese Women

ObjectiveBreast cancer is one of the most frequent cancers among women.Breast density,a reflection of breast tissue composition in mammogram,is reported to be associated with breast cancer risk.Higher breast density has repeatedly been shown to be associated with increased risk of breast cancer among White,African American and Asian American women,but there is currently no information available for Mainland Chinese women.The study accompanied to presents the distribution of mammographic density and examines the associations between known and suspected breast cancer risk factors and breast density among a large number of Chinese women.To examine the possible ethnic differences in mammographic density,variations in densities between Chinese women and other ethnicities were also evaluated.MethodsAsymptomatic women from Beijing,Tianjin,Shenyang and Nanchang city enrolled the study.Study performance was started from 2008 to 2010.(1)A face-to-face interview questionnaire was used to collect information regarding demographical data,reproductive factors,breast disease history,family history of cancer,behavior patterns and social/psychological characteristics.(2)Clinical breast examination(CBE),breast ultrasound(BUS)and mammography(MAM)were performed concurrently.A double-blind method was in place to keep each screening test independent by not informing both the patients and examiners of each preceding result prior to the succeeding tests.Women with suspiciously malignant growths in the breasts detected by any of these three modalities subsequently underwent biopsy to determine malignancy.The negative cases were followed up for a year to confirm negativity.(3)During mammography screening,craniocaudal(CC)and mediolateral oblique(MLO)views were used to calculate density measures.Qualitative assessment was according to the BI-RADS coding system.The density assessments were performed by radiologists who had been trained before.The readers were blinded to all subject characteristics.Randomly select some of the breast X-ray image to re-evaluate for the accuracy and consistency of density assessment.(4)Results of the breast density data were pooled and analyzed.The association between breast density and breast cancer risk,and the association between breast density and potential breast cancer risk factors,were measured by unconditional logistic regression.Odds ratios(ORs)and 95%confidence intervals(CIs)were estimated for the association between mammographic patterns and the selected factors.(5)Variation in the distribution of mammographic density by ethnicity was compared among Chinese,White,Asian American and African American women.Unconditional logistic regression was performed for dense breasts relative to fatty breasts and adjusted OR with 95%CI was calculated.Results(1)Women in this study had a large percentage of "scattered fibroglandular”(37.5%)and“heterogeneously dense”breasts(40.6%),compared with a minority of "almost entirely fat"(12.4%)and "extremely dense" breasts(8.6%).(2)After adjusted by age and BMI,multiple analyses indicated that lower mammographic density was associated with late age of menarche(OR=0.81,95%CI,0.75-0.91),post menopause(OR=0.67,95%CI,0.63-0.72),more parity(OR=0.59,95%CI,0.55-0.64),while higher mammographic density was associated with late age at first birth(OR=1.32,95%CI,1.22-1.43),hormone use(OR=1.30,95%CI,1.06-1.58),benign breast disease(OR=1.60,95%CI,1.52-1.69)and smoking(OR=1.28,95%CI,1.09-1.50).Compared women with almost entirely fatty breasts(BI-RADS 1),women with breasts of scattered fibroglandular densities have a greater breast cancer risk(OR=2.23,95%CI,1.04-4.79).(3)Among women age<50,breasts of Chinese women were denser than that of Caucasian and African American women but more fatty than Asian American women;among women age≥50,breasts of Chinese women were more fatty than that of Caucasian,African American and Asian women.ConclusionsThis study suggests that several risk factors for breast cancer were associated with breast density in Chinese women.Information on the determinants of mammographic density may provide valuable insights into breast cancer aetiology.The breasts of Chinese women were fattier than those of American women in the older age group,but the opposite was found in the younger age group.This study provided parameters of mammographic density in a large nember of Chinese women,which will be a basis for future study and cancer prevention.