Current evidence on breast cancer among US Hispanic women indicates a significant public health threat, although few studies have assessed the heterogeneity in breast cancer risk among Hispanics of different origin.
Current evidence on breast cancer among US Hispanic women indicates a significant public health threat, although few studies have assessed the heterogeneity in breast cancer risk among Hispanics of different origin.
The 2000 and 2005 National Health Interview Survey Cancer Control Modules were used to examine the Breast Cancer Risk Assessment Tool (BCRAT) 5-year risk and lifetime risk of invasive breast cancer among Mexican/Mexican American, Puerto Rican, Cuban/Cuban American, Dominican (Republic), Central/South American, Other Hispanic, and non-Hispanic white (NHW) women ages 35 to 84 years. Multiple linear regression models were used to compare the BCRAT 5-year and lifetime breast cancer risk between 1) Hispanics and NHWs and 2) Hispanic subgroups.
Hispanic women had significantly lower mean BCRAT 5-year and lifetime breast cancer risk compared with NHW women (P < .001). Among Hispanic subgroups, Cuban/Cuban Americans had a higher BCRAT 5-year risk (P < .05), whereas Dominicans had a higher lifetime risk (P < .001) compared with Mexican/Mexican Americans. Approximately 2.6% of Hispanic women were at high risk for breast cancer (BCRAT 5-year risk ≥1.67%), ranging from 1% of Central/South Americans to 3.7% of Puerto Ricans; few Hispanics (0.2%) had a lifetime risk ≥20%.
The current findings indicate that Hispanic women have a significantly lower risk of breast cancer compared with NHW women, although the risk according to BCRAT differed significantly between specific Hispanic subgroups. We provide estimates of the number of US Hispanic women from six subgroups who may be eligible for prophylactic breast cancer chemoprevention. The authors concluded that future studies should further investigate the heterogeneity in breast cancer risk and risk factors between Hispanic women of different origins. Cancer 2013. © 2012 American Cancer Society.
Breast cancer is a significant public health threat to Hispanic women in the United States, as it represents the most frequently diagnosed cancer and the leading cause of cancer-related death in this population.1 Although recent trends indicate a declining incidence of breast cancer among US women, breast cancer incidence has declined at a slower rate for US Hispanic women2; furthermore, these findings are consistent across stages of diagnosis with the rate at which large breast cancer tumors are diagnosed among Hispanic women not declining significantly.3 Despite having a low incidence rate of breast cancer, Hispanic women are more likely to present with advanced breast cancer at diagnosis4, 5 and are more likely to die from breast cancer compared with non-Hispanic white women.6-8
Although these data reflect the burden of breast cancer among Hispanic women as a whole, it is also important to understand the diversity of this population and the extent to which the risk of breast cancer varies between Hispanic women of different national origins and backgrounds. US Hispanic women are characterized by differences in genetic ancestry and in behavioral and lifestyle practices, which may lead to differences in their risk of developing breast cancer.2 However, the heterogeneity in breast cancer risk among women in different Hispanic subgroups has not been well defined.
To address this gap, the objective of the current study was to assess the distribution of breast cancer risk among Hispanic women from six subgroups: Mexican/Mexican Americans, Puerto Ricans, Cubans/Cuban Americans, Dominicans, Central/South Americans, and Other Hispanics. By using data from the 2000 and 2005 National Health Interview Survey (NHIS) Cancer Control Modules (CCMs), we assessed the 5-year and lifetime risk of developing invasive breast cancer among US Hispanic women (n = 3386) and non-Hispanic white women (n = 16,131) based on the National Cancer Institute (NCI) Breast Cancer Risk Assessment Tool (BCRAT). Evaluating breast cancer risk among different Hispanic subgroups has the potential to improve our understanding of the impact of breast cancer in this diverse population and to identify those women from specific Hispanic subgroups who may benefit from strategies to reduce the risk of breast cancer.
Information about the study design, data source, and study population was previously described in detail.9 In brief, the NHIS is an annual, cross-sectional household survey that obtains information on the health of the civilian, noninstitutionalized population residing in the United States.10 The NHIS is a multistage, cluster probability sample survey design that over samples both Hispanic and black populations. Furthermore, the NHIS core questionnaire is comprised of 4 components: household, family, sample adult, and sample child, with additional supplement questionnaires on specific topics, including: cancer control. The CCM, which was designed and funded by the NCI, was administered in 2000 and 2005 and collected information on diet and nutrition, physical activity, tobacco use, cancer screening, genetic testing, family history, and other risk factors related to cancer. The 2000 and 2005 NHIS CCMs collected data from 1 randomly sampled adult aged ≥18 years from each sampled family and household, resulting in 32,374 and 31,321 sampled adults, respectively. For the current study, we analyzed data on Hispanic women (n = 3386) and non-Hispanic white women (n = 16,131) ages 35 to 84 years who had no history of breast cancer or mastectomy (unilateral or bilateral) and who completed the CCM module.
Absolute risk is defined as the probability that an individual with a given set of risk factors who is free of the disease of interest at age x (eg, age 40 years) will develop the disease before a subsequent age x + y (eg, age 45 years), where y is the time interval over which risk is projected11 (eg, 5 years). The NCI BCRAT12, 13 (available at: http://www.cancer.gov/bcrisktool/; [accessed July 1, 2012]) estimates a woman's absolute risk of developing invasive breast cancer over a specific time based on age, age at first live birth, age at menarche, number of first-degree relatives with breast cancer, number of breast biopsies, and presence of atypical hyperplasia (note that information on atypical hyperplasia is unavailable in the NHIS). When information on a particular risk factor is missing, BCRAT imputes the lowest category of risk. We used the BCRAT to estimate participants' absolute risk of invasive breast cancer over two periods: 1) 5-year risk, calculated from the age at interview to the hypothetical age that a woman would attain if she survived for 5 years after the date of the interview; and 2) lifetime risk, calculated from the age at interview to the hypothetical age that a woman would attain if she survived to age 90 years.
The 2000 and 2005 NHIS collected self-reported data on race and Hispanic origin (based on country of origin and ancestry), which we used to categorize women as non-Hispanic white or Hispanic. Hispanic women were further divided into six distinct subgroups: Mexican/Mexican Americans, Cubans/Cuban Americans, Puerto Ricans, Dominicans, Central or South Americans, and other Latin Americans/other Spanish/multiple Hispanics (referred to as “Other Hispanics”).
We included several variables in the analyses that previous research indicates may be associated with the risk of developing breast cancer.14-22 Sociodemographic variables included marital status (married/living with intimate partner or other), education (less than high school graduate, high school graduate/General Education Development [GED], or more than high school), and federal poverty level (<100%, 100%-200%, or ≥200%). Two variables were included as proxies for access to health care: usual source of care (yes or no) and insurance status (private, public, or uninsured). We also included information on county of birth (US born or foreign born), years in the United States (<5 years, 5-9 years, or ≥10 years), and language most often spoken (mostly/only Spanish, Spanish/English about the same, or mostly/only English), and body mass index (BMI) (normal, BMI <25 kg/m2; overweight, BMI 25-30 kg/m2; or obese, BMI >30 kg/m2).
Data from the 2000 and 2005 NHIS were pooled for this analysis. To obtain US population estimates, the observations were weighted by the sample weights for each year, which were summed and divided by 2.23 The stratified, multistage cluster complex sample design of the NHIS was accounted for when calculating standard errors and 95% confidence intervals.23
Descriptive statistics were used to assess participants' baseline sociodemographic, access, acculturation, and BMI characteristics. We estimated participants' BCRAT 5-year and lifetime risk estimates and corresponding 95% confidence intervals, as previously described.12, 13 Statistical methods appropriate for complex samples were used to compare the distribution of descriptive variables between non-Hispanic white women and Hispanic women and between Hispanic subgroups including the t test, the chi-square test, and the Wald F test.
Multiple linear regression models were then estimated for both the BCRAT 5-year and lifetime absolute breast cancer risk estimates, separately, controlling for the explanatory variables. For each risk estimate, 2 different comparisons were made: 1) between Hispanics versus non-Hispanic whites and 2) among Hispanic subgroups. A 3-step multiple imputation method, which was used previously in an analysis of a US-based population health survey, as previously described,24 was used to impute poverty level, because approximately 24% of the observations were missing these values. First, we estimated an ordinal logistic regression model for poverty level using marital status, education, and Hispanic subgroup combined with country of birth/time in the United States. Second, for each individual with missing poverty level data, we generated probability cutoff points for each category of poverty level based on regression model coefficients. Third, we drew a random number between zero and 1 from a uniform distribution and compared it with the probability cutoff points to assign each individual to 1 category. It is noteworthy that the National Center for Health Statistics also generated imputed income variables for both the 2000 and 2005 NHIS surveys,25 although, we used the previously described method for the current study.
In addition, we used a stepwise approach to the regression models using four different models. Model 1 was adjusted for marital status, age, education, and federal poverty level; Model 2 was adjusted for the Model 1 covariates plus usual source of care and insurance; Model 3 was adjusted for Model 2 covariates plus BMI; and Model 4 was adjusted for Model 3 covariates plus country of origin and years in the United States. For the acculturation variables, a composite variable was generated that combined county of birth (US born, foreign born) and years in the United States (<5 years, 5-9 years, ≥10 years). Bivariate analyses indicated that the language most often spoken was not predictive of breast cancer risk and, accordingly, was dropped from the final regression analyses. All computations were conducted using SAS software (version 9.2; SAS Institute Inc, Cary, NC) and SAS callable SUDAAN (version 9.0; RTI, Research Triangle Park, NC).
The mean age of non-Hispanic white women was significantly older compared with that of Hispanic women (54.3 years vs 50.3 years, respectively; P < .001) (Table 1). Overall, a significantly greater proportion of Hispanic women were aged <12 years at initiation of menarche, younger at first live birth, had no family history of breast cancer, and had never received a breast biopsy compared with non-Hispanic white women. Further, a significantly greater proportion of Hispanic women had less than a high school education (46%) and had a household income that was <100% of the federal poverty level (21.7%) compared with non-Hispanic white women (11.9% and 6.8%, respectively).
|Percentage of Patients|
|Characteristic||Non-Hispanic Whites, n = 16,131||Total Hispanics, n = 3386||Mexicans/ Mexican Americans, n = 1932||Puerto Ricans, n = 385||Cubans/ Cuban Americans, n = 274||Dominicans, n = 123||Central/ South Americans, n = 468||Other Hispanics, n = 204)|
|BCRAT risk factors|
|Mean age [95% CI], y||54.3 [54.1-54.3]||50.3 [49.7-50.9]a||49.8 [48.9-50.6]b||51 [49.5-52.4]||56.5 [54.5-58.4]||48 [45.7-50.3]||48 [46.7-49.3]||52.8 [50.2-55.5]|
|Age at menarche, y|
|Age at first live birth, yr|
|No. of first-degree relatives with breast cancer|
|No. of previous breast biopsies|
|Years in the US|
|Marital status. %|
|Married/living with partner||68.8||66.1a||69.1b||55.3||63.4||51.3||68.7||64.9|
|Usual source of care|
|Body mass index|
Among Hispanic subgroups, Cuban/Cuban American women had the highest mean age (56.5 years). A greater proportion of Mexican/Mexican American women (48.3%) and Other Hispanic women (86.5%) were born in the United States, whereas Puerto Rican women had the greatest proportion that spoke only/mostly Spanish (27.4%). Puerto Rican women (91.4%) and Other Hispanic women (93.8%) had the greatest proportion with a usual source of care, and Central/South American women had the greatest proportion of uninsured women (52.8%). Mexican/Mexican American women (36.4%) and Puerto Rican women (36.7%) had the greatest proportion of obese women among Hispanic subgroups.
Table 2 presents the mean 5-year and lifetime BCRAT absolute risk estimates of study participants. These results indicate that, for the Hispanic women in our study, on average, the probability of developing invasive breast cancer over the next 5 years was 0.64%, and, over their lifetime, it was 5.88%, which was significantly lower than the risks for non-Hispanic white women (1.24% and 8.63%, respectively; P < .001). Among Hispanic women, Cuban/Cuban American and Other Hispanic women had a significantly higher mean BCRAT 5-year absolute risk compared with Mexican/Mexican American women (P < .001). Dominican and Central/South American women had a significantly higher mean BCRAT lifetime absolute risk compared with Mexican/Mexican American women (P < .001).
|Participant Subgroup||Total No.||BCRAT 5- Year Risk||BCRAT Lifetime Risk|
|Non-Hispanic whites||53,600,388||1.24 [1.23-1.26]||8.63 [8.56-8.70]|
|All Hispanics||6,616,996||0.64 [0.62-0.66]b||5.88 [5.77-5.99]b|
|Mexican/Mexican Americans||3,682,494||0.62 [0.60-0.65]||5.83 [5.70-5.95]|
|Puerto Ricans||795,878||0.67 [0.60-0.74]||5.82 [5.53-6.10]|
|Cubans/Cuban Americans||523,990||0.83 [0.76-0.89]c||5.47 [5.14-5.80]|
|Dominicans||198,432||0.62 [0.54-0.70]||6.68 [6.17-7.18]c|
|Central/South Americans||1,034,701||0.59 [0.55-0.62]||6.23 [5.95-6.51]c|
|Other Hispanics||381,500||0.70 [0.64-0.75]c||5.71 [5.15-6.27]|
A significantly lower proportion of Hispanic women were at high risk of breast cancer compared with non-Hispanic white women (P < .001) (Table 3) based on both the BCRAT 5-year risk and lifetime risk estimates (eg, threshold values for identifying women at high-risk, as defined by the American Society of Clinical Oncology [ASCO] and the National Comprehensive Cancer Network [NCCN], of ≥1.67% 5-year risk of invasive breast cancer and ≥20% lifetime risk of invasive breast cancer). Approximately 2.6% of all Hispanic women had a BCRAT 5-year absolute risk ≥1.67%, and only 0.2% had a lifetime absolute risk ≥20%. Central/South American women had a significantly lower proportion of women at high risk of breast cancer (1%) compared with Mexican/Mexican American women (2.7%; P < .001). Among Hispanic subgroups, few women had a BCRAT lifetime absolute risk ≥20%, and only 0.4% of Other Hispanic women and 0.3% of Mexican/Mexican American women met this high-risk threshold.
|5-Year Risk ≥1.67%||Lifetime Risk ≥20%|
|Participant Subgroup||No.||% [95% CI]||No.||% [95% CI]|
|Non-Hispanic whites||10,479,744||19.55 [18.84-20.26]||730,723||1.36 [1.16-1.56]|
|All Hispanics||171,484||2.59 [1.98-3.20]b||11,425||0.17 [0.03-0.31]b|
|Mexican/Mexican Americans||99,227||2.69 [1.91-3.47]||10,008||0.27 [0.03-0.50]|
|Puerto Ricans||29,801||3.74 [0.71-6.74]||—c||—c|
|Cubans/Cuban Americans||15,874||3.03 [1.09-4.97]||—c||—c|
|Dominicans||6210||3.13 [−1.34, 7.60]||—c||—c|
|Central/South Americans||10,426||1.01 [0.32-1.70]d||—c||—c|
|Other Hispanics||9948||2.61 [0.73-4.49]||1417||0.37 [−0.35, 1.09]|
Table 4 summarizes results from the multivariate regression models, indicating that Hispanic women had significantly lower 5-year and lifetime absolute risk of developing breast cancer based on the BCRAT compared with non-Hispanic white women (P < .001). The mean 5-year absolute risk of invasive breast cancer for Hispanic women was consistently lower than for non-Hispanic white women (difference, 0.4 percentage points; P < .001), whereas the mean lifetime absolute risk of invasive breast cancer for Hispanic women was approximately 2.8 percentage points lower than for non-Hispanic white women (P < .001).
|β Estimate (SE)a|
|BCRAT 5-Year Risk||BCRAT Lifetime Risk|
|Participant Subgroup||Model 1||Model 2||Model 3||Model 4||Model 1||Model 2||Model 3||Model 4|
|All Hispanics||−0.41 (0.01)b||−0.41 (0.01)b||−0.41 (0.01)b||−0.42 (0.02)b||−2.86 (0.07)b||−2.81 (0.07)b||−2.79 (0.07)b||−2.77 (0.08)b|
|Puerto Rican||0.02 (0.03)||0.01 (0.03)||0.00 (0.03)||0.01 (0.03)||0.02 (0.14)||−0.00 (0.14)||−0.06 (0.14)||−0.00 (0.14)|
|Cuban/Cuban Americans||0.05 (0.02)c||0.05 (0.03)c||0.04 (0.03)||0.05 (0.03)c||0.18 (0.17)||0.16 (0.18)||0.11 (0.18)||0.15 (0.18)|
|Dominicans||0.02 (0.03)||0.01 (0.03)||0.02 (0.03)||0.03 (0.03)||0.73 (0.21)d||0.75 (0.23)c||0.82 (0.25)d||0.85 (0.26)d|
|Central/South Americans||−0.02 (0.03)||−0.01 (0.02)||−0.01 (0.02)||0.01 (0.02)||0.04 (0.11)||0.05 (0.12)||0.07 (0.12)||0.12 (0.12)|
|Other Hispanics||−0.00 (0.03)||−0.01 (0.03)||−0.01 (0.03)||−0.01 (0.03)||−0.19 (0.21)||−0.20 (0.21)||−0.23 (0.22)||−0.23 (0.22)|
With regard to Hispanic women, the 5-year absolute risk of breast cancer for Cuban/Cuban American women was higher than the risk for Mexican/Mexican American women (P < .05). No other differences in BCRAT 5-year absolute risk were observed between Mexican/Mexican American women and other Hispanic subgroups. In assessing the lifetime absolute risk of breast cancer, the mean risk for Dominican women was significantly higher than the mean risk for Mexican/Mexican American women, and the difference remained significant after controlling for all covariates (P < .001). There were no other differences observed in lifetime absolute risk when comparing Other Hispanic subgroups with Mexican/Mexican American women.
Comparing all Hispanics with non-Hispanic whites, age, education, poverty level, insurance status, and BMI were all significantly associated with women's 5-year absolute risk of breast cancer (results not shown). In particular, increased age, having public health insurance, and being overweight/obese were all associated with significant increases in the 5-year absolute risk. Similar trends were observed for the lifetime absolute risk of breast cancer, although increased age was associated with a significantly lower lifetime absolute risk of breast cancer. In comparisons between Hispanic subgroups, age, marital status, education, poverty level, insurance status, and years in the United States were associated significantly with the 5-year absolute risk of breast cancer (results not shown). Specifically, women from the same Hispanic subgroup who had lived in the United States for less than 5 years had a significantly lower 5-year absolute risk of breast cancer compared with women who were born in the United States (P < .05), controlling for all other covariates. This association was not observed for the lifetime risk of breast cancer.
Building on the current literature, the current study was a broad assessment of the absolute risk of developing breast cancer among different subgroups of Hispanic women. Our findings indicate that, among Hispanic women overall, the 5-year and lifetime absolute risks of developing invasive breast cancer, based on the BCRAT, were significantly lower compared with the risks among non-Hispanic white women. Among Hispanic subgroups, Cuban/Cuban American women had a greater BCRAT 5-year absolute risk of developing invasive breast cancer, whereas Dominican women had a greater BCRAT lifetime absolute risk of developing invasive breast cancer. Factors that were associated with differences in breast cancer risk among Hispanic subgroups included age, education, health insurance status, usual source of care, poverty level, and length of residence in the United States. Furthermore, the proportion of Hispanic women who may be eligible for breast cancer risk-reduction strategies, such as the receipt of prophylactic tamoxifen and raloxifene, based on ASCO and NCCN guidelines, ranges from approximately 1% of Central/South American women to 4% of Puerto Rican women.
Consistent with previous reports,26 we observed that Hispanic women have a significantly lower 5-year and lifetime absolute risk of developing invasive breast cancer based on the BCRAT. Furthermore, the magnitude by which Hispanic women's breast cancer risk was lower than non-Hispanic white women's risk remained significant and relatively constant, even after multivariate adjustment for key risk factors. These findings suggest that other factors, either unidentified and/or unmeasured in our analysis, may help explain the differences observed in BCRAT risk estimates between Hispanic women and non-Hispanic white women.
Evidence regarding the risk of developing breast cancer among Hispanic women has highlighted differences between US-born and foreign-born women.17 Results from the San Francisco Bay Area Women's Breast Cancer Study demonstrated that foreign-born Hispanic, postmenopausal women had a significantly lower risk of breast cancer compared with their US-born counterparts. Our current study expands on this finding by evaluating differences in risk by Hispanic subgroup, and the results indicate that, compared with Mexican/Mexican American women, Cuban/Cuban American women have a significantly higher 5-year risk of breast cancer, whereas Dominicans have a significantly higher lifetime risk of breast cancer. Consequently, although BCRAT risk among Other Hispanic subgroups did not differ, the increased risk among Cuban/Cuban American women and Dominican women may reflect other important underlying factors, such as genetic ancestry,27 that account for differences in BCRAT estimates of the risk of developing invasive breast cancer among these Hispanic subgroups.
Our finding of lower breast cancer risk in foreign-born Hispanic women who have <5 years of residence in the United States further strengthens the importance of birthplace, migration, and length of residence in the United States as factors associated with breast cancer risk among Hispanic women.17, 28 Therefore, migration-related changes experienced by Hispanic women who move to the United States, such as those to hormones and lifestyle factors (ie, weight gain or changes in diet), may have important ramifications for the risk of developing breast cancer.
It is noteworthy that our study is among the first, if not the only, to provide an estimate of the proportion and number of women from different Hispanic subgroups who may be eligible to receive prophylactic tamoxifen and raloxifene. Both the ASCO and the NCCN recommend that patients who meet the high-risk threshold of BCRAT 5-year risk ≥1.67% are eligible for, and may consider, counseling about prophylactic tamoxifen or raloxifene to reduce the risk of developing invasive breast cancer in the future.29, 30 Thus, as indicated by our findings, up to 2.7% of Mexican American women (approximately 99,000 women) and 3.7% of Puerto Rican women (approximately 30,000 women), among others, may benefit from risk-reduction counseling to consider their options for preventing the onset of breast cancer.
In interpreting the results from this study, it is important to acknowledge its strengths and limitations. The NHIS is a large, population-based study, which allowed us to explore US Hispanic women; however, our study was limited by small samples of women from certain Hispanic subgroups. Nevertheless, these findings build on previous studies of breast cancer risk among different subgroups of Hispanic women, adding considerably to the sparse literature documenting the heterogeneity of the Hispanic population. A possible limitation of this study is that the NHIS is a cross-sectional study; therefore, we are not able to draw any causal inference regarding the relation between breast cancer risk and the risk factors that were included in our analysis. Another limitation is the use of the NCI BCRAT to estimate breast cancer risk in Hispanic women, since evidence suggests it may underestimate risk in this population.31 Despite such underestimation, our findings represent a conservative estimate of breast cancer risk among Hispanic women and the number of women in each subgroup who may benefit from risk-reduction strategies.
In summary, our findings indicate that, based on the BCRAT, Hispanic women have a significantly lower absolute risk of developing invasive breast cancer compared with non-Hispanic white women; furthermore, we highlight differences in the BCRAT risk among women in different Hispanic subgroups. Although country of origin and length of residence were associated significantly with BCRAT risk estimates in our study sample, it is imperative to further investigate how Hispanic ancestry and migration affect women's risk factors for developing breast cancer. Finally, we provide national estimates of the number of Hispanic women, from six key subgroups, who would be eligible for counseling to consider risk reduction by prophylactic breast cancer chemoprevention, as recommended by the ASCO and the NCCN. Future studies are warranted that further investigate the impact of breast cancer among Hispanics of different ancestry along with other important breast cancer risk factors, such as history of cancer in second-degree and higher degree relatives in this population.
Dr. Banegas conducted this work while he was at the University of Washington and Fred Hutchinson Cancer Research Center and was supported in part by the National Cancer Institute Biobehavioral Cancer Prevention and Control Training Program (grant R25CA092408) at the University of Washington and by the National Cancer Institute Center for Hispanic Health Promotion Training Program (grant U54CA153502) at the Fred Hutchinson Cancer Research Center.
CONFLICT OF INTEREST DISCLOSURES
The authors made no disclosures.