Comparison of mammographic densities and their determinants in women from Japan and Hawaii

Abstract

Breast cancer incidence increases considerably in women who migrate from Japan to the United States. Based on the hypothesis that mammographic density in healthy mammograms reflects differences in breast cancer risk, we compared mammographic density in 3 groups of women at different levels of risk: Caucasian and Japanese women in Hawaii and Japanese women in Japan. In a cross-sectional design, preand postmenopausal women without a history of breast cancer and with a mammogram free of suspicious lesions were recruited in mammography clinics and completed a selfadministered questionnaire. Cranio-caudal mammograms were scanned into a computer and the densities measured using a computer-assisted method. Statistical analyses included ANOVA and multiple linear regression. Breast size among women of Japanese ancestry was similar in Hawaii and Japan but 50% smaller than that among Caucasian women. Dense areas were smallest among women in Japan, intermediate among Japanese women in Hawaii and largest among Caucasian women. Percent densities were greater in Japanese women than Caucasian women because of the larger breast sizes in Caucasians. However, percent densities were significantly higher among Japanese women in Hawaii than in Japan. These results indicate that the size of the total breast differs primarily by ethnicity and the size of the dense areas differs mainly by place of residence. Therefore, when comparing ethnic groups with distinct physical proportions, the absolute size of the dense areas appears to be a better measure of breast cancer risk than the relative density. © 2002 Wiley-Liss, Inc. Key words: mammographic density; Japan; Hawaii; breast cancer; mammogramBreast cancer incidence among women in Japan is much lower than among women of Japanese ancestry living in the United States. Age-adjusted (to the world standard population) incidence rates were 30.8 cases/100,000 in Japan 1 compared to 78.3 and 97.1 cases/100,000 among women of Japanese and Caucasian ancestry in Hawaii, respectively (unpublished report for 1990 -1992 from the Hawaii Tumor Registry). Reasons for the discrepant breast cancer rates are not well understood, but the fact that risk in migrants increases over 2 or 3 generations 2,3 suggests that environmental factors, including diet, 4 may be determinants of risk in addition to the well-established reproductive factors, adult adiposity, weight change and height. 5 Mammographic density patterns, which refer to the distribution of fat, connective and epithelial tissue in the healthy female breast, have been related to breast cancer risk. 6 A high percentage of dense parenchyma on mammographic images appears to confer a 4-fold risk of developing breast cancer. 7 Immigration from Japan to Hawaii occurred primarily during 1868 -1924, 8 when more than 200,000 Japanese came to Hawaii. We hypothesized that Japanese women in Hawaii are more likely to have a dense parenchymal pattern than women in Japan. The primary objective of our cross-sectional study was to compare mammographic density charact...

Life course breast cancer risk factors and adult breast density (United Kingdom)

“…The results relating reproductive events (nulliparity, age at first birth, number of children) to breast density are in accordance with data previously reported [23][24][25]. Those studies demonstrate consistent patterns of association between these well-recognised breast cancer risk factors [6] and breast density, irrespective of the manner in which density is assessed (BI-RADS, Tabar, percent area density) across ethnically diverse populations.…”

“…Previous studies have found the opposite [23,31] or no association [24,25], as in the current study. The close proximity to reporting and occurrence of menarche in our study gives greater weight to our finding as its timing is likely to have been accurately recalled over the short period since its occurrence.…”

Breast cancer risk factors and a novel measure of volumetric breast density: cross-sectional study

“…Previous studies have found positive relationships between age at menarche and breast density (El-Bastawissi et al, 2000;Sala et al, 2000), although in this and other previous studies (Jakes et al, 2000;Maskarinec et al, 2002;Heng et al, 2004) such associations have not been demonstrated. Lower parity and later age at first pregnancy are two of the most consistently reported risk factors for breast cancer (Kelsey et al, 1993), and have also been shown to be related to breast density in later life (Heine and Malhotra, 2002), most recently using both SCC and SMF methods in a sample of 250 women in England (McCormack et al, 2007).…”

A Longitudinal Investigation of Mammographic Density: The Multiethnic Cohort

“…Because the amounts of epithelial and stromal tissue as represented by the dense areas probably determine breast cancer risk (3), the size of the dense areas may provide more relevant information than percent density which is strongly influenced by body weight (38,(42)(43)(44). Nonetheless, as Fig.…”