Contrasting Epidemiology and Clinicopathology of Female Breast Cancer in Asians vs the US Population

Ching-Hung Lin; Yoon Sim Yap; Kyung-Hun Lee; Seock-Ah Im; Yoichi Naito; Winnie Yeo; Takayuki Ueno; Ava Kwong; Huiping Li; Shu-Min Huang; Roland Leung; Wonshik Han; Benita Tan; Fu-Chang Hu; Chiun-Sheng Huang; Ann-Lii Cheng; Yen-Shen Lu


J Natl Cancer Inst. 2019;111(12):1298-1306. 

In This Article

Abstract and Introduction


Background: The incidence of breast cancer among younger East Asian women has been increasing rapidly over recent decades. This international collaborative study systemically compared the differences in age-specific incidences and pathological characteristics of breast cancer in East Asian women and women of predominantly European ancestry.

Methods: We excerpted analytic data from six national cancer registries (979 675 cases) and eight hospitals (18 008 cases) in East Asian countries and/or regions and, for comparisons, from the US Surveillance, Epidemiology, and End Results program database. Linear regression analyses of age-specific incidences of female breast cancer and logistic regression analyses of age-specific pathological characteristics of breast cancer were performed. All statistical tests were two-sided.

Results: Unlike female colorectal cancer, the age-specific incidences of breast cancer among East Asian women aged 59 years and younger increased disproportionally over recent decades relative to rates in US contemporaries. For years 2010–2014, the estimated age-specific probability of estrogen receptor positivity increased with age in American patients, whereas that of triple-negative breast cancer (TNBC) declined with age. No similar trends were evident in East Asian patients; their probability of estrogen receptor positivity at age 40–49 years was statistically significantly higher (odd ratio [OR] = 1.50, 95% confidence interval [CI] = 1.36 to 1.67, P < .001) and of TNBC was statistically significantly lower (OR = 0.79, 95% CI = 0.71 to 0.88, P < .001), whereas the probability of ER positivity at age 50–59 years was statistically significantly lower (OR = 0.88, 95% CI = 0.828 to 0.95, P < .001). Subgroup analyses of US Surveillance, Epidemiology, and End Results data showed similarly distinct patterns between East Asian American and white American patients.

Conclusions: Contrasting age-specific incidences and pathological characteristics of breast cancer between East Asian and American women, as well as between East Asian Americans and white Americans, suggests racial differences in the biology.


Although Asian women have lower incidence rates of invasive breast cancer than Western women, the incidence of female breast cancer in East and Southeast Asia has increased rapidly over the past 40 years.[1–3] Previous age-period-cohort analyses showed a strong cohort effect on female breast cancer incidence in Asia,[4,5] which has resulted in notable differences in age-specific incidences of breast cancer between Asian and Western females. Specifically, the incidence of breast cancer peaked at around age 50 years in Hong Kong, Japan, Korea, and Taiwan compared to approximately 70 years in the United States.[2,3,6,7] Incidence rates of breast cancer among younger women in some East Asian populations have even surpassed that of recent generations in the United States.[8]

This strong cohort effect suggests that lifestyle and environmental changes might be major influences on the pathogenesis of breast cancer in Asian women. Rapidly increasing breast cancer incidence in East Asia has primarily been attributed to "Westernization" including: 1) dietary factors (eg, high fat intake, low vegetable consumption, and low soybean intake) and 2) reproductive factors (eg, delayed childbearing, low parity, less breastfeeding, early menarche, and late menopause).[9,10] If rising breast cancer incidence rates were simply due to Westernization, emerging age-specific patterns in modern Asian women would eventually resemble those of Western populations. Therefore, a recent study showed longitudinal age-specific incidence rates with converging incidence rate ratios and concluded that the age effects for invasive breast cancer were more similar among Asian and Western populations than might be expected according to the extrapolated estimates.[8] However, some evidence suggests racial effects on breast carcinogenesis and tumor biology in younger women. For example, overweight and/or obesity were inversely associated with premenopausal breast cancer risk in Europids and African Americans, but positively correlated in Asian women.[11,12] A meta-analysis of breast cancer risk found a protective effect of soybean consumption in Asian and Asian American women, but not in Europids.[13] Additionally, 13 genetic polymorphisms associated with breast cancer in Europeans failed to discriminate breast cancer risk in Singaporean Chinese, Malays, or Indians.[14] Recently, multi-omics profiling of breast cancers in younger Korean patients has revealed distinctive molecular signatures, suggesting a more immune-active tumor microenvironment compared with that of Western counterparts.[15]

Given the highly debatable issue about the similarity or dissimilarity in epidemiology and tumor biology of young female breast cancer between East Asia and Western countries, we conducted this multiregion study and explored the underlying pathophysiologic factors. We systematically compared temporal trends in age-specific incidences and pathological characteristics of female breast cancer among East Asians, Asian Americans, and non-Asian Americans. Female colorectal cancer was used as a control for the effect of Westernized lifestyle.[16,17]