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. Author manuscript; available in PMC: 2023 Feb 1.
Published in final edited form as: Cancer Epidemiol. 2021 Nov 30;76:102076. doi: 10.1016/j.canep.2021.102076

Breast cancer incidence trends in Asian women aged 20 or older as compared to other ethnic women in the United States from 2000 to 2018 by time period, age and tumor stage

Xianglin L Du 1,*, Lulu Song 1
PMCID: PMC8817625  NIHMSID: NIHMS1760991  PMID: 34861613

Abstract

Background:

After new cancer data are released in April 2021, it is important to update the incidence trend in breast cancer from 2000 to 2018 and focus on ethnic disparities in the risk of developing breast cancer.

Methods:

We identified 1,129,564 women who were diagnosed with incident breast cancer at age ≥20 in 2000–2018 from 18 SEER (Surveillance, Epidemiology, and End Results) registries. We utilized the SEER*Stat software to calculate age-adjusted incidence rates.

Results:

Overall age-adjusted incidence rate of breast cancer was the highest in non-Hispanic white (NHW) women (190.4 cases per 100,000 women), followed by NH-black (NHB) (178.4), Asian/Pacific-Islanders (API) (141.3), Hispanic (133.3) and American-Indians/Alaska-Native (AIAN) women (128.8). Annual percentage change (APC) from 2000 to 2018 showed that annual increase was statistically significant for API (APC: 1.0, 95% CI: 0.8–1.3), NHB (APC: 0.5, 0.2–0.7), AIAN (1.6, 1.1–2.2), and Hispanic women (0.4, 0.2–0.7), but annual percentage of incidence did not significantly decrease for NHW (−0.1, −0.4 to −0.1). Incidence rates of hormone-receptor positive breast cancer increased from 2000 to 2018 in all ethnic women, while incidence rates of hormone-receptor negative breast cancer decreased. NHW and NHB women had a significantly higher risk of having breast cancer than API women. In 2012–2018, the risks of having local stage and distant stage breast cancer for NHW (1.31, 1.29–1.33 and 1.19, 1.16–1.21) and NHB (1.09, 1.07–1.11 and 1.31, 1.28–1.35) women were significantly higher than that of API women.

Conclusions:

The incidence of hormone-receptor positive breast cancer increased in all ethnic women from 2000 to 2018 while the incidence of hormone-receptor negative breast cancer decreased. There were still substantial racial disparities in breast cancer incidences.

Keywords: breast cancer, incidence rate, incidence trend, racial disparities, SEER areas

International studies have shown consistently that the incidence of female breast cancer was much higher in women of Europe and north America than in Asian women.1–11 For example, age-standardized female breast cancer incidence rates in 2006–2007 were 95.3, 94.5 and 88.6 cases per 100,000 women for the Netherland, France and USA as compared to 43.3, 43.2, and 25.6 cases per 100,000 women for Japan, China, and Thailand, respectively.2 These higher incidence rates were attributed to multiple factors, including low parity, delayed marriage and childbirth, low breast feeding, increased cancer screening, work and life related stress, lack of exercise, higher obesity rate, higher alcohol consumption and smoking, and differential food intakes.12–28 However, the increasing incidence in breast cancer in Asian women have been observed over the past 3 decades,2,29–35 largely due to adaption of western-style diets and lifestyle.2 Some international and migration studies found that those Asian women who immigrated to Europe or north America had higher breast cancer incidence rates than those women who continued to live in Asia,1 supporting the importance of environmental and lifestyle factors in the etiology of breast cancer. For example, Gomez and colleagues31 reported that age-adjusted incidence rates of invasive breast cancer increased for both US-born and foreign-born Asians from 1988 to 2004. The incidence rate was 120.6 cases per 100,000 person-years for US-born Asians and 76.3 cases for foreign-born Asians with the incidence rate ratio between US-born and foreign-born Asians at 1.58 (95% confidence interval of 1.53–1.63).31 A recent analysis based on the 18 SEER registries data showed that overall breast cancer incidence rates increased among Asian/Pacific Islander (1.7% per year), non-Hispanic black (0.4% per year), and Hispanic women (0.3% per year) but were stable in non-Hispanic white and American Indian/Alaska Native women between 2005 and 2014.9 From 2012 to 2016, the overall increase in breast cancer incidence in women was observed, which largely reflected a rise in local (early) stage disease.10 Our current study aimed to not only provide more detailed analyses on more recent breast cancer incidence trends from 2000 to 2018 by time periods, age groups and tumor stages, but also examine racial disparities in the risk of developing breast cancer by adjusting for age and stage in the regression models.

Methods

Data sources

The National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Public Use Data Set released in November 2020 were used for this study.36 The SEER program supports population-based tumor registries in nine areas (San Francisco/Oakland, San Jose-Monterey, Los Angeles, Greater California, Detroit, Seattle, Atlanta, Rural Georgia, and Greater Georgia) and 9 states (Alaska, Connecticut, Iowa, New Mexico, Utah, Hawaii, Louisiana, Kentucky, and New Jersey), accounting for 28% of the U.S. population. The estimated completeness of cancer case reporting in SEER areas was 97.7%.37 The SEER registries ascertain all newly diagnosed (incident) cancer cases from multiple reporting sources such as hospitals, outpatient clinics, laboratories, private medical practitioners, nursing/convalescent homes/hospices, autopsy reports and death certificates. Information includes tumor location and size; lymph node and distant organ metastases; histologic type and grade of tumor; demographic characteristics such as age, gender, race and marital status; and type of treatments provided in the first course of therapy within four months of initial therapy after diagnosis. This study was considered exempt for Institutional Review Board (IRB) review because it did not involve any patient contact and only had the analysis of de-identified SEER Public Use Data.

Study Population

Our study identified 1,129,564 women who were diagnosed with incident breast cancer at age 20 or older between 2000 and 2018 in 18 SEER registries. The denominator of population data included all women aged 20 or older in the same SEER areas that were provided in the SEER*Stat package.36 Of the 1,129,564 women with breast cancer, 802,790 were non-Hispanic whites (NHW), 119,175 were non-Hispanic blacks (NHB), 86,461 were non-Hispanic Asians/Pacific Islanders (API), 115,309 were Hispanic women, and 5,829 were American Indians and Alaska Natives (AIAN).

Study Variables

Race/ethnicity variable was classified into NHW, NHB, API, Hispanics, and AIAN. The patient socio-demographics included age at diagnosis (20–44, 45–54, 55 or older), year of diagnosis (2000 to 2018), and geographic areas (18 SEER registries). Tumor stage included local, regional, or distant stage. Hormone receptor positive breast cancer was defined if estrogen or progesterone receptor was positive.

Statistical Analysis

We utilized the SEER*Stat software (version 8.3.9) that was provided by the National Cancer Institute together with the SEER Data for analyses in cancer incidence rates and trends. Incidence of breast cancer in women was defined as a ratio of the number of women with a new breast cancer over the number of total female population at risk in the same SEER areas by year, which was presented in number of cases per 100,000 persons. Because age is a significant risk factor for cancer incidence, the incidence rates of breast cancer in all comparison groups by race/ethnicity or time periods that may consist of different age compositions should be standardized by age. Therefore, in this study the incidence rates were adjusted to the year 2000 standard US population by age. The age-adjusted incidence rates, 95% confidence intervals for incidence rates, incidence rate ratios ((IRR) and their 95% confidence intervals and annual percentage change (APC) of incidence rates were calculated from the SEER*Stat software. A p value <0.05 was considered statistically significant.

Results

Table 1 presents the number of total female population, number of incident breast cancer cases, and unadjusted and age-adjusted incidence rates in Asian women and other racial/ethnic women aged 20 or older in all 18 SEER areas in 2000–2018. The overall age-adjusted incidence rate of breast cancer was the highest in NHW women (190.4 cases per 100,000 women), followed by NHB (178.4), API (141.3), Hispanic (133.3) and AIAN women (128.8). The incidence rate ratio was statistically significantly higher in NHW (rate ratio: 1.35, 95% CI: 1.34–1.36) and NHB women (1.26, 1.25–1.27), but was significantly lower in Hispanic women (0.94, 0.94–0.95) and AIAN women (0.91, 0.89–0.94) as compared to API women.

Table 1.

Number of population, number of incident breast cancer cases, and breast cancer incidence in Asian women and other racial/ethnic women in all SEER areas, 2000–2018

Race/Ethnicity Number of population Number of breast cancer cases Unadjusted Incidence rates (N of cases per 100,000) (95% CI) Age-adjusted* incidence rates (N of cases per 100,000) (95% CI) Rate ratio (between age-adjusted incidence rates) (95% CI)
Non-Hispanic Asians and Pacific Islanders 61,849,358 86,461 139.8 (138.9–140.7) 141.3 (140.3–142.2) 1.00 (reference)
Non-Hispanic white 356,020,637 802,790 225.5 (225.0–226.0) 190.4 (190.0–190.8) 1.35 (1.34–1.36)
Non-Hispanic black 69,761,330 119,175 170.8 (169.9–171.8) 178.4 (177.4–179.4) 1.26 (1.25–1.27)
American Indians and Alaska Natives 4,779,347 5,829 122.0 (118.9–125.1) 128.8 (125.4–132.3) 0.91 (0.89–0.94)
Hispanics 110,049,635 115,309 104.8 (104.2–105.4) 133.3 (132.5–134.1) 0.94 (0.94–0.95)
Total 602,460,307 1,129,564 187.5 (187.1–187.8) 176.9 (176.5– 177.2)
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*

Incidence rates were age adjusted to the 2000 US population.

Trend analyses showed that only NHW women had a decreasing trend in overall breast cancer incidence rates from 2000 to 2018, whereas all other ethnic women had a slightly increasing trend in breast cancer incidence rates (Figure 1). Table 2 presents the incidence rates and their changes by three time periods in calendar years for various ethnic women. Overall, annual percentage change (APC) from 2000 to 2018 showed that annual increase was statistically significant for API (APC: 1.0, 95% CI: 0.8–1.3), NHB (APC: 0.5, 0.2–0.7), AIAN (1.6, 1.1–2.2), and Hispanic women (0.4, 0.2–0.7) (see last column in Table 2). Overall annual percentage of incidence decreased but not significantly for NHW (−0.1, −0.4 to −0.1). Because the incidence appeared to increase after 2009, we also showed the most recent and available data on the trends from 2010 to 2018 by race/ethnicity in Supplement Figure S1 and Supplement Table S1, indicating significant increasing trend for API, NHW, and Hispanic women, but no significant change for NHB and AIAN. Table 3 presents the age-adjusted incidence rates by race/ethnicity that was stratified by hormone receptor status. The age-adjusted incidence rates of hormone receptor positive breast cancer increased over time from 2000 to 2018 in all race/ethnic women with no exception. The annual percentage change of incidence increase was greater in AIAN and NHB women, followed by API, Hispanic and NHW women. For hormone receptor negative breast cancer or hormone receptor unknown or at borderline, the incidence rates were decreasing over time in all ethnic women. The largest annual percentage decrease was observed in NHW women with hormone receptor unknown or at borderline breast cancer (−13.1%).

Figure 1.

Figure 1.

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Trends in age-adjusted incidence rates (number of breast cancer cases per 100,000 population) in women by race/ethnicity in SEER areas from 2000 to 2018

Table 2.

Annual percentage change (APC) in age-adjusted incidence rates* (number of breast cancer cases per 100,000 population) in women by time period and race/ethnicity

Race/Ethnicity 2000–2005 2006–2011 2012–2018 APC (95% CI) P value
N. Population N. Cases Incidence rate (95% CI) N. Population N. Cases Incidence rate (95% CI) N. Population N. Cases Incidence rate (95% CI)
Non-Hispanic Asians and Pacific Islanders 15,862,213 19,459 132.2 (130.3–134.1) 19,186,258 25,720 136.8 (135.1–138.5) 22,800,887 41,282 149.2 (147.7–150.7) 1.0 (0.8, 1.3) < 0.05
Non-Hispanic white 111,747,980 243,792 193.0 (192.3–193.8) 112,106,666 249,339 188.6 (187.9–189.4) 132,163,991 309,659 190.5 (189.8–191.2) −0.1 (−0.4, −0.1) 0.2
Non-Hispanic black 20,115,429 30,973 171.0 (169.0–172.9) 21,705,448 36,874 178.1 (176.3–180.0) 27,940,453 51,328 183.1 (181.5–184.8) 0.5 (0.2, 0.7) < 0.05
American Indians and Alaska Natives 1,403,381 1,407 114.7 (108.5–121.1) 1,492,543 1,773 125.5 (119.3–131.7) 1,883,423 2,649 139.9 (134.5–145.5) 1.6 (1.1, 2.2) < 0.05
Hispanics 28,316,058 26,214 130.3 (128.6–131.9) 34,412,281 34,460 130.1 (128.7–131.5) 47,321,296 54,635 137.0 (135.9–138.2) 0.4 (0.2, 0.7) < 0.05
Total 177,445,061 321,845 179.1 (178.5–179.7) 188,905,196 348,166 174.9 (174.3–175.5) 236,110,050 459,553 177.1 (176.6–177.6) −0.1 (−0.3, −0.1) 0.3
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*

Incidence rates were age adjusted to the 2000 US population.

Table 3.

Annual percentage change (APC) in age-adjusted incidence rates (number of breast cancer cases per 100,000 population) in women in 2000–2018 by hormone receptor status and race/ethnicity

Race/Ethnicity Hormone-receptor positive Hormone-receptor negative Hormone-receptor status unknown or borderline
N. Cases Incidence rate (95% CI) APC (95% CI) from 2000 to 2018 N. Cases Incidence rate (95% CI) APC (95% CI) from 2000 to 2018 N. Cases Incidence rate (95% CI) APC (95% CI) from 2000 to 2018
Non-Hispanic Asians and Pacific Islanders 66,990 109.5 (108.7, 110.4) 2.5 (2.2, 2.7) 13,786 22.3 (21.9, 22.7) −0.6 (−1.1, 0.0) 5,685 9.4 (9.2, 9.7) −10.5 (−11.8, −9.1)
Non-Hispanic white 620,197 146.6 (146.2, 147.0) 1.4 (1.2, 1.7) 113,751 28.0 (27.9, 28.2) −1.3 (−1.9, −0.7) 68,842 15.8 (15.6, 15.9) −12.7 (−13.8, −11.6)
Non-Hispanic black 75,918 114.1 (113.3, 115.0) 2.8 (2.3, 3.3) 31,706 46.5 (46.0, 47.1) −0.3 (−1.0, 0.4) 11,551 17.7 (17.4, 18.1) −11.9 (−13.0, −10.8)
American Indians and Alaska Natives 4,474 96.5 (93.5, 99.5) 3.0 (2.2, 3.8) 1,004 21.9 (20.5, 23.3) −0.3 (−1.7, 1.1) 451 10.5 (9.5, 11.5) −6.3 (−8.6, −4.0)
Hispanics 83,682 97.7 (97.0, 98.4) 2.2 (1.9, 2.6) 21,316 23.3 (22.9, 23.6) −0.8 (−1.6, −0.1) 10,311 12.3 (12.1, 12.6) −10.1 (−11.5, −8.6)
Total 851,161 133.1 (132.8,133.4) 1.5 (1.2, 1.7) 181,563 28.8 (28.7, 28.9) −1.1 (−1.6, −0.5) 96,840 15.0 (14.9, 15.1) −12.1 (−13.3, −10.9)
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*

Incidence rates were age adjusted to the 2000 US population. Hormone-receptor positive was defined as estrogen-receptor was positive OR progesterone receptor was positive.

Table 4 presents the age-adjusted incidence rates by race/ethnicity that was stratified by 3 age groups and 3 time periods. In all age groups regardless of young (20–44 years), middle age (45–54), or older age (>=55 years), and in all time periods (2000–2005, 2006–2011, and 2012–2018), NHW and NHB women had a significantly higher risk of having breast cancer than API women. The magnitude of the incidence rate ratio was greater in women aged 55 or older for NHW (1.69, 1.66–1.72) and NHB (1.40, 1.37–1.44) women as compared to APIs, while the incidence rate ratio was smaller in younger women less than 45 years for NHW (1.09, 1.06–1.12) and NHB (1.17, 1.12–1.22) women in the time period of 2000–2005. The risk of having breast cancer in AIAN and Hispanic women was generally significantly lower than that of API women aged 20–44 and 45–54 years. Interestingly, in women aged 55 or older AIAN women had no significantly different risk of breast cancer while Hispanic women had a significantly higher risk of breast cancer than API women in the earlier time periods of 2000–2005 and 2006–2011. However, in 2012–2018, both AIAN and Hispanic women aged 55 or older had no significantly different risks of breast cancer as compared to API women. In middle-age women of 45–54 years, AIAN and Hispanic women still had a significantly lower risk of breast cancer than API women, but in younger women less than 45 years, only Hispanic women but not AIAN women had a significantly lower risk of breast cancer than API women.

Table 4.

Age-adjusted incidence rates (number of breast cancer cases per 100,000 women) by age groups, race/ethnicity, and time period

Race/Ethnicity Age 20–44 yrs Age 45–54 yrs Age ≥55 yrs
N. Population N. Cases Incidence rate (95% CI) Rate ratio (95% CI) N. Population N. Cases Incidence rate (95% CI) Rate ratio (95% CI) N. Population N. Cases Incidence rate (95% CI) Rate ratio (95% CI)
2000–2005
Non-Hispanic Asians and Pacific Islanders 8,720,162 3,663 45.3 (43.8, 46.8) 1.00 (ref) 3,050,172 5,628 184.5 (179.7, 189.4) 1.00 (ref) 4,091,879 10,168 247.5 (242.7, 252.4) 1.00 (ref)
Non-Hispanic white 49,156,031 25,126 49.2 (48.6, 49.8) 1.09 (1.05, 1.13) 22,354,647 50,484 225.0 (223.1, 227.0) 1.22 (1.19, 1.25) 40,237,302 168,182 418.3 (416.3, 420.3) 1.69 (1.66, 1.72)
Non-Hispanic black 11,228,415 5,656 52.9 (51.6, 54.3) 1.17 (1.12, 1.22) 3,864,214 8,104 210.1 (205.5, 214.7) 1.14 (1.10, 1.18) 5,022,800 17,213 347.7 (342.5, 353.0) 1.40 (1.37, 1.44)
American Indians and Alaska Natives 789,144 258 34.2 (30.2, 38.7) 0.76 (0.67, 0.86) 289,763 425 146.9 (133.2, 161.5) 0.80 (0.72, 0.88) 324,474 724 231.6 (214.5, 249.8) 0.94 (0.86, 1.01)
Hispanics 18,853,130 5,778 36.7 (35.7, 37.6) 0.81 (0.78, 0.84) 4,459,288 7,188 162.2 (158.5, 166.0) 0.88 (0.85, 0.91) 5,003,640 13,248 269.9(265.3, 274.7) 1.09 (1.06, 1.12)
Total (2000–2005) 88,746,882 40,481 46.9 (46.5, 47.4) 34,018,084 71,829 210.9 (209.4, 212.5) 54,680,095 209,535 384.6 (383.0, 386.3)
2006–2011
Non-Hispanic Asians 9,865,153 4,339 46.9 (45.5, 48.3) 1.00 (ref) 3,677,948 6,979 189.3 (184.9, 193.8) 1.00 (ref) 5,643,157 14,402 257.1 (252.8, 261.4) 1.00 (ref)
Non-Hispanic white 44.816,003 22,417 51.3 (50.7, 52.0) 1.10 (1.06, 1,13) 22,828,283 50,544 220.2 (218.3, 222.1) 1.16 (1.13, 1.19) 44,464,380 176,378 403.0 (401.1, 405.0) 1.57 (1.54, 1.60)
Non-Hispanic black 11,158,040 5,731 55.7 (54.2, 57.1) 1.19 (1.14, 1.24) 4,421,680 9,192 207.4 (203.1, 211.7) 1.10 (1.06, 1.13) 6,125,728 21,951 368.8 (363.8, 373.8) 1.43 (1.40, 1.47)
American Indians and Alaska Natives 763,242 254 37.5 (33.0, 42.4) 0.80 (0.70, 0.91) 320,396 462 143.9 (131.1, 157.7) 0.76 (0.69, 0.84) 408,905 1,057 264.2 (247.8, 281.4) 1.03 (0.96, 1.10)
Hispanics 21,536,450 6,801 36.8 (35.9, 37.7) 0.78 (0.76, 0.82) 5,993,616 9,515 159.2 (156.0, 162.5) 0.84 (0.82, 0.87) 6,882,215 18,144 271.0 (267.0, 275.1) 1.05 (1.03, 1.08)
Total (2006–2011) 88,138,888 39,542 48.0 (47.5, 48.5) 37,241,923 76,692 205.1 (203.7, 206.6) 63,524,385 231,932 372.4 (370.9, 374.0)
2012–2018
Non-Hispanic Asians 13,058,803 6,160 49.5 (48.3, 50.8) 1.00 (ref) 4,828,472 10,180 210.5 (206.4, 214.6) 1.00 (ref) 8,913,612 24,942 280.7 (277.2, 284.3) 1.00 (ref)
Non-Hispanic white 50,295,413 24,146 52.9 (52.2, 53.5) 1.07 (1.04, 1.10) 23,638,499 53,601 224.4 (222.5, 226.3) 1.07 (1.04, 1.09) 58,230,079 231,912 404.1 (402.4, 405.7) 1.44 (1.42, 1.46)
Non-Hispanic black 13,690,032 6,549 55.2 (53.9, 56.6) 1.12 (1.08, 1.16) 5,214,970 11,247 213.8 (209.8, 217.8) 1.02 (0.99, 1.04) 9,035,451 33,532 382.2 (378.0, 386.4) 1.36 (1.34, 1.38)
American Indians and Alaska Natives 916,560 334 44.1 (39.5, 49.2) 0.89 (0.80, 1.00) 347,538 566 161.2 (148.1, 175.1) 0.77 (0.70, 0.83) 619,325 1,749 290.0 (276.0, 304.5) 1.03 (0.98, 1.09)
Hispanics 27,662,537 9,644 40.5 (39.7, 41.4) 0.82 (0.79, 0.86) 8,461,741 14,126 166.9 (164.2, 169.7) 0.79 (0.77, 0.81) 11,197,018 30,865 282.9 (279.6, 286.2) 1.01 (0.99, 1.03)
Total (2012–2018) 105,623,345 46,833 49.6 (49.1, 50.0) 42,491,220 89,720 209.5 (208.1, 210.9) 87,995,485 323,000 374.3 (373.0, 375.6)
Total (2000–2018) 282,509,115 126,856 48.2 (48.0, 48.5) 113,751,227 238,241 208.4 (207.6, 209.3) 206,199,965 764,467 376.5 (375.7, 377.4)
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*

Incidence rates were age adjusted to the 2000 US population in each of the 3 age groups.

Table 5 presents the age-adjusted incidence rates by race/ethnicity that was stratified by tumor stages and time periods. In all tumor stages across 3 different time periods, NHW and NHB women had a significantly higher risk of having breast cancer than API women. For example, NHW and NHB women had a significantly higher risk of having local stage breast cancer (1.47, 1.44–1.49, and 1.07, 1.05–1.10) and distant stage breast cancer (1.68, 1.58–1.78 and 2.51, 2.35–2.69) as compared to API women in 2000–2005. In 2012–2018, the risks of having local stage and distant stage breast cancer for NHW (1.31, 1.29–1.33 and 1.19, 1.16–1.21) and NHB (1.09, 1.07–1.11 and 1.31, 1.28–1.35) women were still significantly higher than that of API women. However, there were some different interesting observations in AIAN and Hispanic women, in which both AIAN and Hispanic women had a significantly lower risk of having local stage breast cancer but had a significantly higher risk of having distant stage breast cancer than API women across the 2000–2005 and 2006–2011 periods. For example, the risk of having local stage breast cancer was 0.83 (0.77–0.89) for AIAN and 0.89 (0.87–0.91) for Hispanic women, but the risk of having distant stage breast cancer was 1.40 (1.15–1.70) for AIAN and 1.33 (1.24–1.44) for Hispanic women as compared to API women in 2000–2005. In 2012–2018, AIAN women had a significantly lower risk of having local stage breast cancer (0.90, 0.85–0.95) but had no significant risk of regional or distant stage breast cancer, whereas Hispanic women had a significantly lower risk of having local stage (0.85, 0.83–0.86) and distant stage (0.94, 0.91–0.96) breast cancer but had a significant higher risk of regional stage (1.06, 1.04–1.09) breast cancer as compared to API women.

Table 5.

Age-adjusted incidence rates (number of breast cancer cases per 100,000 population) in women by tumor stage, Asian sub-groups and time period

Race/Ethnicity Local stage Breast Cancer Regional Stage Breast Cancer Distant Stage or Unknown Breast Cancer
N. Population N. Cases Incidence rate (95% CI) Rate ratio (95% CI) N. Cases Incidence rate (95% CI) Rate ratio (95% CI) N. Cases Incidence rate (95% CI) Rate ratio (95% CI)
2000–2005
Non-Hispanic Asians and Pacific Islanders 15,862,213 11,960 81.8 (80.4, 83.3) 1.00 (reference) 6,362 42.4 (41.4, 43.5) 1.00 (reference) 1,137 7.9 (7.4, 8.4) 1.00 (reference)
Non-Hispanic white 111,747,980 152,325 120.0 (119.4, 120.6) 1.47 (1.44, 1.49) 73,938 59.8 (59.4, 60.2) 1.41 (1.37, 1.45) 17,529 13.3 (13.1, 13.5) 1.68 (1.58, 1.78)
Non-Hispanic black 20,115,429 15,764 87.9 (86.5, 89.3) 1.07 (1.05, 1.10) 11,689 63.2 (62.1, 64.4) 1.49 (1.45, 1.54) 3,520 19.9 (19.2, 20.5) 2.51 (2.35,2.69)
American Indians and Alaska Natives 1,403,381 817 67.9 (63.1, 73.0) 0.83 (0.77, 0.89) 461 35.6 (32.3, 39.2) 0.84 (0.76, 0.93) 129 11.1 (9.2, 13.3) 1.40 (1.15, 1.70)
Hispanics 28,316,058 14,230 72.8 (71.6, 74.1) 0.89 (0.87, 0.91) 9,983 46.9 (45.9, 47.9) 1.10 (1.07, 1.14) 2,001 10.6 (10.1, 11.0) 1.33 (1.24, 1.44)
Total (2000–2005) 177,445,061 195,096 108.6 (108.1, 109.1) 102,433 57.3 (56.9, 57.6) 24,316 13.3 (13.1, 13.5)
2006–2011
Non-Hispanic Asians 19,186,258 16,368 87.3 (86.0, 88.7) 1.00 (reference) 7,616 40.2 (39.3, 41.1) 1.00 (reference) 1,736 9.2 (8.8, 9.7) 1.00 (reference)
Non-Hispanic white 112,108,666 160,071 120.2 (119.6, 120.8) 1.38 (1.35, 1.40) 70,887 55.1 (54.7, 55.5) 1.37 (1.34, 1.40) 18,381 13.3 (13.1, 13.5) 1.44 (1.37, 1.51)
Non-Hispanic black 21,705,448 19,653 95.6 (94.2, 97.0) 1.09 (1.07, 1.12) 13,138 62.6 (61.5, 63.7) 1.56 (1.51, 1.60) 4,083 20.0 (19.3, 20.6) 2.16 (2.04, 2.29)
American Indians and Alaska Natives 1,492,543 1,009 71.9 (67.4, 76.7) 0.82 (0.77, 0.88) 615 42.8 (39.4, 46.5) 1.07 (0.98, 1.16) 149 10.7 (9.0, 12.7) 1.16 (0.97, 1.38)
Hispanics 34,412,281 19,395 75.1 (74.0, 76.2) 0.86 (0.84, 0.88) 12,253 44.2 (43.4 45.0) 1.10 (1.07, 1.13) 2,812 10.8 (10.4, 11.2) 1.17 (1.10, 1.25)
Total (2006–2011) 188,905,196 216,496 108.6 (108.1, 109.0) 104,509 52.9 (52.6, 53.3) 27,161 13.4 (13.2, 13.6)
2012–2018
Non-Hispanic Asians 22,800,887 22,476 80.9 (79.8, 82.0) 1.00 (reference) 9,598 34.9 (34.2, 35.6) 1.00 (reference) 9,208 33.4 (32.7, 34.1) 1.00 (reference)
Non-Hispanic white 132,163,991 176,308 106.9 (106.4, 107.4) 1.31 (1.29, 1.33) 67,988 44.0 (43.7, 44.4) 1.26 (1.23, 1.29) 65,363 39.6 (39.3, 39.9) 1.19 (116, 1.21)
Non-Hispanic black 27,940,453 24,811 88.3 (87.2, 89.5) 1.09 (1.07, 1.11) 14,287 51.0 (50.1, 51.8) 1.46 (1.42, 1.50) 12,230 43.8 (43.0, 44.6) 1.31 (1.28, 1.35)
American Indians and Alaska Natives 1,883,423 1,409 73.7 (69.8, 77.8) 0.90 (0.85, 0.95) 645 34.4 (31.8, 37.3) 0.99 (0.91, 1.07) 595 31.8 (29.2, 34.5) 0.95 (0.87, 1.04)
Hispanics 47,321,296 26,003 68.7 (67.8, 69.5) 0.85 (0.83, 0.86) 15,325 37.1 (36.5, 37.7) 1.06 (1.04, 1.09) 12,307 31.2 (30.7, 31.8) 0.94 (0.91, 0.96)
Total (2012–2018) 236,110,050 252,007 96.2 (95.8, 96.6) 107,843 42.7 (42.4, 42.9) 99,703 38.2 (38.0, 38.5)
Total (2000–2018) 602,460,307 663,599 103.5 (103.2, 103.8) 314,785 50.0 (49.8, 50.2) 151,180 23.4 (23.3, 23.5)
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*

Incidence rates were age adjusted to the 2000 US population.

Discussion

This study examined the most recent breast cancer incidence trends among women in SEER areas from 2000 to 2018 by time periods, age groups and tumor stages, and explored racial disparities in the risk of developing breast cancer by adjusting for multiple confounding factors. Our study found that only NHW women had a decreasing trend in breast cancer incidence rates overall from 2000 to 2018, whereas all other ethnic women had a slightly increasing trend in breast cancer incidence. The decreasing trend in breast cancer incidence rates for NHW women was largely driven by the decreasing number of hormone receptor unknown or at borderline breast cancer. In those with hormone receptor positive breast cancer, there was actually a small increase from 2000 to 2018 in NHW women. The incidence rate ratio was statistically significantly higher in NHW and NHB women as compared to API women, but was significantly lower in Hispanic women an AIAN women. However, although AIAN and Hispanic women had a significantly lower risk of having early stage (local stage) breast cancer, they had a significantly higher risk of having distant stage breast cancer than API women in 2000–2018.

Our study on the most recent cohort of breast cancer cases in SEER areas of the United States supported the findings of previous incidence trend studies.8–10,29–35 For example, DeSantis and colleagues9 found that overall breast cancer incidence rates from 2005 to 2014 increased among API (1.7% per year), NHB (0.4% per year), and Hispanic women (0.3% per year) but were stable among NHW and AIAN women in SEER areas. Gomez and colleagues31 showed that breast cancer incidence rates increased over time from 1988 to 2004 among Asian women in California and the incidence increase was greater in the US-born Asian populations than in those foreign-born Asian women. Tuan and colleagues35 reported an increasing trend of breast cancer incidence among Asian women and in most subgroups of Asians such as Filipina, South Asian, Chinese, Korean, and Vietnamese women from 1990 to 2014 in SEER areas, but incidence rates did not change significantly during this time period for NHW and Japanese women. Several other studies also demonstrated an increasing trend in incidence rates for overall breast cancer and for some subtypes of breast cancer in Asian women in the United States.29–35

The decreasing trend in NHW women was primarily attributed to the decreased use of menopausal hormones following the publication and recommendation of two large clinical trial results in 2002, which concluded that hormone replacement therapy was associated with a higher risk of heart disease and breast cancer.3,8–11 It may also be due to small declines in mammography screening since 2000.3,8–11 The increasing trend in other ethnic women, particularly among API women, may be attributed to adaption of western-style diets and lifestyle, more work and life-related stress, lack of physical exercise, increases in body mass index, and declines in the average number of births per woman.4,13–28,37 The improved technology and accuracy in cancer diagnosis and imaging may also have made the previously undetected metastatic tumors or unknown tumor stages to be defined now, hence leading to an increased incidence.

Our study and many previous studies8–11,38 consistently demonstrated that the risk of developing breast cancer was higher in NHW and NHB women, and lower in API, AIAN and Hispanic women. A particular interesting finding was that AIAN and Hispanic women had a lower risk of having early stage breast cancer but had a higher risk of having distant (late) stage breast cancer than in API women. The reasons for these racial/ethnic disparities in the risk of developing breast cancer are multifactorial and might include the lack of physical exercise, higher body mass index, increased work and life related stress, higher alcohol consumption and smoking, delayed marriage and childbirth, lower breast feeding, lower parity, and higher utilization of hormone birth control pills and postmenopausal hormone medications.11,13–28 Although breast cancer incidence rates are increasing in women in all racial/ethnic women except for NHW women, good news is that the mortality rates for breast cancer are decreasing over the past decades due to improvements in early detection and in treatment.11 However, many challenges are still ahead of us in order to address and narrow substantial disparities in cancer incidence and in mortality.

This study has several limitations to be kept in mind for interpretation. First, because there was no information on the place of birth and time of migration for breast cancer cases and for population denominator, the study cannot address the cancer incidence disparities by U.S.-born or foreign-born women or by the timing of migration for those women who immigrated from other countries. Second, although there were some differences among the subgroups of API women such as Chinese, Korean and Japanese Americans, or among the subgroups of Hispanic women such as Mexican or Cuban Americans, the cancer incidence rates by these subgroups cannot be addressed due to lack of information from the population denominators in SEER*Stats data system. Third, many potential risk factors for breast cancer such as parity, smoking, physical exercise, and hormone use differed substantially by race and ethnicity, but breast cancer incidence rates by race/ethnicity duo to these differences cannot be controlled for in the analyses. Fourth, the study found that AIAN and Hispanic women had a significantly higher risk of having distant stage breast cancer than API women in 2000–2018. This may be related to a lower breast cancer mammogram screening rate, as studies showed that in 2018 only 66% of AIAN women had mammogram screening in last two years as compared to 71% of API women aged 50–74 years.40 However, this association cannot be determined in this study due to lack of screening data. Finally, although there was information on health insurance status for cancer cases, this factor cannot be taken into consideration in the analyses because of lack of such information in population denominators.

In conclusion, we observed a slightly increasing trend in overall breast cancer incidence for all ethnic women except for NHW women who had a decreasing trend from 2000 to 2018, but we also observed a small increase in the incidence of hormone receptor positive breast cancer among NHW women and a decreasing trend of hormone receptor negative or unknown breast cancer for all ethnic women. There were still substantial racial disparities in breast cancer incidence with the higher risk of breast cancer in NHW and NHB women and the lower risk in AIAN, Hispanic and API women. AIAN and Hispanic women had a significantly lower risk of having early stage breast cancer but had a significantly higher risk of having distant stage breast cancer than API women. There are still many challenges ahead for us to mitigate risk factors for decreasing breast cancer incidence and to reduce racial disparities for cancer burden.

Supplementary Material

Supp.Materials

Highlights.

  • Hormone-receptor positive breast cancer incidence rates increased in all ethnic women

  • Decreasing trend of hormone receptor negative or unknown breast cancer in 2000–2018

  • Breast cancer incidence was higher in white and black women than Hispanics and Asians

  • Hispanics had a lower risk of early stage but higher risk of distant stage breast cancer

Acknowledgments

Research reported in this publication was supported by the National Institute On Aging of the National Institutes of Health under Award Number R01AG058971 and R01AG067498. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Disclosures and Declarations, Compliance with Ethical Standards

This study was supported by the NIH grant Number R01AG058971 and R01AG067498. There are no conflicts of interest from all authors.

Footnotes

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