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

Abstract

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.

Figure 1.

Age-specific incidence rates of female breast and colorectal cancers in East Asia and the United States and in SEER Asian Americans and non-Hispanic white Americans. A) The observed age-specific incidence rates of female breast cancer in East Asia (n = 253 840) and the United States (n = 66 230) for years 2011–2014. B) The observed age-specific incidence rates of female colorectal cancer in East Asia (n = 184 055) and the United States (n = 17 688) for years 2011–2014. C) The estimated age-specific incidence rates of female breast cancer in East Asia and the United States for years 2011–2014. D) The estimated age-specific incidence rates of female colorectal cancer in East Asia and the United States for years 2011–2014. The estimated age-specific incidence rates shown in (C) and (D) were based on the fitted multiple linear regression models in Supplementary Table 1 (available online). E) The observed age-specific incidence rates of female breast cancer in SEER Asian Americans (n = 25 665) and non-Hispanic white Americans (n = 683 164) for years 1990–2010. F) The observed age-specific incidence rates of female colorectal cancer in SEER Asian Americans (n = 11 982) and non-Hispanic white Americans (n = 240 286) for years 1990–2010. SEER = Surveillance, Epidemiology, and End Results.

Figure 2.

Observed age-specific probabilities of ER+ (A), HER2+ (B), TNBC (C), and histological grade III (D) female breast cancer in East Asia and the United States. Age-specific clinicopathological characteristics of female breast cancer were determined based on 18 008 cases from hospital data in East Asian countries and/or regions and 244 819 cases from US SEER data for years 2010–2014. BCH = Beijing Cancer Hospital; ER+ = estrogen receptor positive; HER2+ = human epidermal growth factor receptor 2 positive; KUH = Kyorin University Hospital; NCCHE = National Cancer Center Hospital East; NCCS = National Cancer Centre Singapore; NTUH = National Taiwan University Hospital; PWH = Prince of Wales Hospital; SGH = Singapore General Hospital; SNUH = Seoul National University Hospital; TNBC = triple-negative breast cancer; WCD = West Cluster Database.

Figure 3.

Conditional effect plots of estimated age-specific probabilities of ER+ (A), HER2+ (B), TNBC (C), and histological grade III (D) female breast cancer in East Asia and the United States for years 2010–2014. The estimated age-specific clinicopathological characteristics of female breast cancer were determined based on the fitted multiple logistic regression models of 18 008 cases in East Asians and 244 819 in Americans (Supplementary Table 2, available online). ER+ = estrogen receptor positive; HER2+ = human epidermal growth factor receptor 2 positive; TNBC = triple-negative breast cancer.

Figure 4.

Observed age-specific proportions of ER+ (A), HER2+ (B), TNBC (C), and histological grade III (D) female breast cancer in Surveillance, Epidemiology, and End Results program Asian Americans and white Americans for years 2010–2013. The age-specific proportions of ER+, HER2+, TNBC, and histological grade III between 7185 C-J-K Asian Americans and 194 524 white Americans were compared using two-sided pointwise two-sample z tests. The figures show the exact P values when P < .05. C-J-K = Chinese-Japanese-Korean; ER+ = estrogen receptor positive; HER2+ = human epidermal growth factor receptor 2 positive; TNBC = triple-negative breast cancer.