Racial/ethnicity disparities in invasive breast cancer among younger and older women: An analysis using multiple measures of population health

Abstract

Introduction

Few studies have examined age and racial/ethnic disparities in invasive breast cancer among younger (age 15–44 years) vs. older (age 45–64 years) women. This study estimates disparities in breast cancer among younger compared with older women by race/ethnicity using five measures of population health: life expectancy (LE), expected years of life lost (EYLL), cumulative incidence rate (CIR), and incidence and mortality rate ratios (IRR and MRR).

Methods

Using Surveillance, Epidemiology, and End Results data, LE and EYLL were estimated from a cohort of 15–44 and 45–64 years, non-Hispanic black (NHB), non-Hispanic white (NHW), and Hispanic women diagnosed with breast cancer, 2000–2013. Survival function was obtained from the study years and then extrapolated to lifetime using the Monte Carlo method. The CIR, IRR and MRR were calculated using 2009–2013 breast cancer incidence and mortality rates from the Centers for Disease Control and Prevention’s National Program of Cancer Registries.

Results

The estimated LE ranged from 32.12 to 7.42 years for localized to distant stages among younger NHB women compared to 33.05 to 9.95 years for younger NHW women. The estimated EYLL was 12.78 years for younger women, and 4.99 for older women. By race/ethnicity, it was 15.53 years for NHB, 14.23 years for Hispanic and 11.87 years for NHW (P <0.00025). The CIR for age-group 15–44 years (CIR_15–44 indicated a 1 in 86 probability for NHB compared to a 1 in 87 probability for NHW being diagnosed with breast cancer by age 45. The estimated age-adjusted incidence rate for NHB-to-NHW women was IRR = 1.10 (95%, CI = 1.08–1.11) and the corresponding mortality rate was MRR = 2.02 (95%, CI = 1.94–2.11).

Conclusions

The breast cancer disparities between younger NHB compared to NHW women highlight the need for expanded efforts to address these disparities through primary prevention and to improve access to quality healthcare to minority women with breast cancer.

1. Introduction

Breast cancer is the most common malignant tumor among U.S. women, accounting for 30% of incident cancers [1]. Despite the benefits of advances in treatment and early detection that have contributed to the decline in breast cancer deaths [2], not all age and racial/ethnic groups have benefited equally and disparities in incidence and mortality still exist [3]. Further, several studies have examined age disparities in breast cancer outcomes [4–9]. These studies have reported substantially lower health-related quality of life resulting from breast cancer treatment in younger (i.e., aged 15–44 years) compared with older (i.e., aged 45–64 years) women. Similarly, studies have reported racial/ethnic disparities in breast cancer outcomes [10–13]. These studies found that black women are more likely than white women to have late-stage breast cancer at diagnosis and have less favorable outcomes, including higher mortality rates [10,11]. In addition, other studies have also found that both younger and older black women have higher mortality rates than any other racial/ethnic group [12,13].

In recent years, there has been public health initiative in breast cancer among younger women. More specifically, the Education and Awareness Requires Learning Young (EARLY) Act, Section 10413 of the Affordable Care Act [Public Law 111–148]) [14] has renewed interest in how the risk of breast cancer impacts younger women. Currently, no studies have examined age (younger versus (vs) older) and racial/ethnic disparities (that is, non-Hispanic black (NHB), non-Hispanic white (NHW), and Hispanic women) using multiple measures of population health, which includes life expectancy (LE), expected years of life lost (EYLL), cumulative incidence rates for women ages 15–44 and 45–64 years (CIR_{15–44,45–64}), and age-adjusted incidence and mortality rate ratios (IRR and MRR). However, the impact of breast cancer disparities have been quantified using other population-based measures developed to evaluate cancer progress in national health objectives [15–17].

In this paper, we utilized multiple measures of population health (i.e., LE, EYLL, CIR, IRR, and MRR), to determine 1) whether breast cancer burden was greater for younger vs older women; 2) to estimate the magnitude of racial/ethnic disparities in invasive breast cancer among younger NHB vs NHW women, and younger Hispanic vs NHW women; and 3) to examine whether racial/ethnic disparities in incidence and mortality of breast cancer among younger women are worse in breast cancer than in all other female cancers. Each of these measures contributes differently in providing information to patients, clinicians, and health policy-makers on the burden of breast cancer disparities in age-and racial/ethnic-groups. We hope that the use of these measures may provide useful data for outcome assessment and resource allocation of health services and development of prevention strategies for age- and racial/ethnic-groups that are disproportionately more likely to develop breast cancer in their lifetime.

2. Methods

2.1. Data sources and study population

Data from the National Cancer Institute (NCI)’s 2000–2013 Surveillance, Epidemiology, and End Results (SEER-18) registries [18], which covers 28% of the US population, were used to estimate LE and EYLL. The SEER-18 registries were used because it contains survival information needed to estimate these measures [18]. A cohort of 88,406 women aged 15–44 and 345,025 women aged 45–64 with invasive breast cancer were identified from SEER. In addition, the combined dataset from the Centers for Disease Control and Prevention (CDC)’s National Program of Cancer Registries (NPCR) and the NCI’s SEER registries [1], which covers the entire U.S. population, were used to estimate CIRs, incidence, and mortality rates for a separate cohort of 113,328 women aged 15–44 and 512,511 women aged 45–64 diagnosed (2009–2013) with invasive breast cancer. These population-based cancer registries collect detailed information on patient’s sex, race/ethnicity, year of diagnosis, age of diagnosis, cancer site, stage, survival months, and vital status [18]. In both datasets, invasive breast cancer was defined by the standards in the International Classification of Diseases for Oncology, 3rd Edition [19]. To minimize confounding of survival times for the primary cancer, patients with a prior breast cancer diagnosis and those diagnosed based on death certificate or autopsy only were excluded (<1%). Death was defined as all-cause mortality; all breast cancer patients were followed until death or through the end of follow-up (December 31, 2013).

2.2. Measures of population health

The LE and EYLL incorporate data on the US life tables to estimate the burden of breast cancer in the population [20]. The estimation of LE from the date of diagnosis until death was used to generate lifetime survival in different racial/ethnic groups (NHB, NHW, and Hispanic) that may be relevant to clinicians in treating breast cancer patients. In estimating LE, we did not include racial/ethnic groups of Asian/Pacific Islander and American Indian/Alaska Native women because of a lack of life tables for these populations.

On the other hand, the estimation of EYLL, which is a measure of the overall burden of disease was used to determine the lifetime health impact of breast cancer in age-and racial/ethnic-groups. These two measures were used to examine the extent to which a younger NHB vs NHW, and younger Hispanic vs NHW woman’s life span was likely to be reduced by breast cancer after diagnosis. The third measure (CIR_{15–44,45–64}) estimated age, and racial/ethnic disparities in the cumulative risk of being diagnosed with breast cancer over a time period and age interval [21] in the population. The last two measures, IRR and MRR, were used to further explore whether racial/ethnic disparity in incidence and mortality of breast cancer among younger women are worse in breast cancer than in all other female cancers [22].

2.3. Calculation of life expectancy (LE)

The Kaplan-Meier method [23] was used to estimate survival function for each cohort of breast cancer patients with 14 years of follow-up. Using a semi-parametric method [24], the estimated survival functions were further extrapolated up to 720 months (60 years) to derive LE after breast cancer diagnosis. The method uses relevant external information to aid the survival extrapolation. Its technical details have been described elsewhere [25]. Briefly, for a breast cancer cohort, the US life tables [26] were used to generate survival times for an age-, sex- and race/ethnicity-matched reference population using a Monte Carlo method. Thesurvival times are then used for estimating survival function of the reference population. Second, with the assumption of excess constant hazard, logit transformation of the survival ratios between the cohort and the reference population will approach a straight line [27]. Hence, a linear regression was fitted to the logit transformed survival ratios during some time period near the end of follow-up. Finally, the estimated regression line and the survival function of the reference population beyond the follow-up limit were used to extrapolate the lifetime survival function of the cohort. The standard errors of the estimated LE were obtained using a bootstrap method.

2.4. Calculation of expected years of life lost (EYLL) per breast cancer patient

EYLL was defined as the reduced LE due to breast cancer in younger vs older women, younger NHB vs NHW women and younger Hispanic vs NHW women from that of the age- sex- and race/ethnicity-matched reference population. It was calculated by taking the difference in the areas under the long-term survival curves between the breast cancer cohort and the reference population as shown in Fig. 1a, b, and c.

Fig. 1.

(a) Estimated expected years of life lost (EYLL) from breast cancer among younger women aged 15–44 years compared with older women aged 45–64 years, SEER registries, 2000–2013.¹ (b) Estimated expected years of life lost (EYLL) from breast cancer among younger non-Hispanic black (NHB) women compared with younger non-Hispanic white (NHW) women, SEER registries, 2000–2013.² (c) Estimated expected years of life lost (EYLL) from breast cancer among younger Hispanic women compared with younger non-Hispanic white (NHW) women, SEER registries, 2000–2013.³

¹The estimated EYLL was 7.79 years (= 12.78–4.99 years) was significantly different between younger and older women with P <0.00025

²The estimated EYLL was 3.66 years (= 15.53–11.87 years) was significantly different between younger NHB women vs. younger NHW women with P <0.00025.

³The estimated EYLL was 2.36 years (= 14.23–11.87 years) was significantly different between younger Hispanic women vs. younger NHW women with P <0.00025

2.5. Calculation of cumulative incidence rates (CIR_{15–44,45–64})

The CIR_{15–44,45–64} was calculated using the most recent five years of data (2009–2013) on breast cancer incidence rates among younger vs older women, younger NHB vs NHW women, and younger Hispanic vs NHW women from the NPCR/SEER registries [1]. The calculation of CIR_{15–44,45–64} was as follows: CIR_{15–44,45–64} = 1−exp [−S_i (IR_i) * (Δt_i)]; where IR_i represents the age-specific incidence rate and Δt_i indicates the range of each age stratum.

2.6. Calculation of breast cancer incidence and mortality rate ratios (IRRs and MRRs)

Using the age-adjusted breast cancer incidence and mortality rates obtained from the 2009–2013 NPCR-SEER registries [1], IRRs and MRRs for younger-to-older, younger NHB-to-NHW and younger Hispanic-to-NHW women were calculated. We also calculated IRRs and MRRs for all other female cancer sites.

2.7. Statistical analysis

The methods described above for estimating LE and EYLL were conducted using the Integration of Survival with Quality of Life (iSQoL) statistical software [28]. Differences in stage distribution and EYLL of breast cancer patients by age-groups and race/ethnicity were tested with chi-square test and one-sided z-tests, with P <0.05 as the level of significance. Further, SEER*Stat software (version 8.3.2) [29] was used to extract age- and race/ethnicity-specific breast cancer incidence, mortality, and associated population data for the years 2009–2013. Rates, expressed per 100,000 population, were directly age-adjusted to the 2000 US standard population [30]. The age-adjusted IRRs and MRRs were also calculated using the age-adjusted rates for younger NHB vs NHW and younger Hispanic vs NHW women. We calculated 95% confidence intervals (CIs) for age-adjusted RRs based on methods described elsewhere [31].

3. Results

Table 1 presents the characteristics of invasive breast cancer by stage, age and race/ethnicity. Overall, the mean age at diagnosis for younger vs older women were 39.02 and 54.86 years, respectively. A significantly greater proportion of younger women (48.13%) were diagnosed at late stages (i.e., regional and distant) compared with older women (38.66%), P <0.0001. By racial/ethnic group, 54.49% of younger NHB women were diagnosed at late stage compared with 45.95% of NHW women, (P <0.0001). Similarly, younger Hispanic women had a higher proportion of late stage diagnosis (52.88%) compared with NHW women, P <0.0001 (Table 1).

Table 1.

Characteristics of invasive breast cancer by stage and race/ethnicity in younger and older women^a, SEER registries, 2000–2013.

	All women			Younger women
	15–44 years	45–64 years	P valueb	NHW	NHB	P valueb	Hispanic	P valueb
Cohort size	88,406	345,025		51,850	12,257		14,221
Mean age at diagnosis (SD)	39.02 (4.53)	54.86 (5.64)		39.31 (4.37)	38.50 (4.84)		38.50 (4.75)
Stage distribution n (%)			<0.0001			<0.0001		<0.0001
Localize	45,856 (51.87)	211,652 (61.34)		28,024 (54.05)	5,578 (45.51)		6,700 (47.12)
Regional	36,542 (41.33)	110,792 (32.11)		20,821 (40.15)	5,381 (43.90)		6,370 (44.79)
Distant	6,008 (6.80)	22,581 (6.55)		3,005 (5.80)	1,298 (10.59)		1,151 (8.09)

SEER: Surveillance, Epidemiology, and End Results; NHW: Non-Hispanic White; NHB: Non-Hispanic Black; SD: standard deviation.

^aYounger women was defined as those aged 15–44 years; Older women was defined as those aged 45–64 years.

^bComparing statistically significant difference of stage distribution between younger vs older women; younger NHB vs younger NHW women, and younger Hispanic vs younger NHW women, P<0.0001.

3.1. Estimated LE and EYLL due to breast cancer

For all women, the estimated LE was higher for younger women, with 33.36, 26.47, and 10.20 years for localized, regional, and distant stages, respectively, compared to estimates for older women, which were 26.26, 20.96, and 6.50 years for localized, regional, and distant stages, respectively, P <0.00025 (Table 2). The estimated LEs were shorter for younger NHB women (32.12, 22.01, and 7.42 years for localized, regional and distant stages, respectively than estimates for NHW women, which were 33.05, 28.77, and 9.95 years for localized, regional, and distant stages, respectively. However, for younger Hispanic women the estimated LEs were longer than for NHW women in localized and distant stages (39.49 vs 33.05 and 12.17 vs 9.95 years), respectively.

Table 2.

Life expectancy (LE), expected years of life lost (EYLL) and cumulative incidence rates (CIR) of younger and older women^a with invasive breast cancer, by stage and race/ethnicity, SEER registries, 2000–2013.

	All women			Younger women
	15–44 years	45–64 years	P valueb	NHW	NHB	P valueb	Hispanic	P valueb
LE, years (SE)c
Localized	33.36	26.26	<0.00025	33.05	32.12	<0.00025	39.49	<0.00025
	(0.03)	0.02		0.03	0.07		0.06
Regional	26.47	20.96	<0.00025	28.77	22.01	<0.00025	25.19	<0.00025
	0.03	0.02		0.04	0.07		0.07
Distant	10.20	6.50	<0.00025	9.95	7.42	<0.00025	12.17	<0.00025
	0.09	0.04		0.11	0.15		0.17
EYLL, years (SE)d
Localized	8.83	1.83	<0.00025	9.30	7.89	<0.00025	5.49	<0.00025
	0.02	0.01		0.02	0.06		0.05
Regional	16.12	7.76	<0.00025	13.95	18.42	<0.00025	20.36	<0.00025
	0.04	0.02		0.04	0.08		0.07
Distant	33.15	21.51	<0.00025	33.44	33.73	> 0.05	33.96	<0.006
	0.10	0.05		0.12	0.14		0.17
CIR15–44,45–64 (2009–2013)e	0.0109	0.0479	<0.05	0.0115	0.0116	> 0.05	0.0076	<0.05

NHW: Non-Hispanic White; NHB: Non-Hispanic Black; SE, standard error of mean.

^aYounger women was defined as those aged 15–44 years; Older women was defined as those aged 45–64 years.

^bComparing statistically significant difference of stage distribution between younger vs older women; younger NHB vs younger NHW women, and younger Hispanic vs younger NHW women.

^cThe survival function for breast cancer cohort was extrapolated through 720 months (60 years) after diagnosis using the semiparametric method to estimate the mean life-expectancy.

^dThe EYLL was calculated by subtracting the estimated life-expectancy of the breast cancer cohort from that of the age-,sex, and race/ethnicity-matched reference population.

^eCumulative incidence rates of breast cancer in younger women between age 15–44 years and older women 45–64 years diagnosed with invasive breast cancer during 2009–2013, NPCR (National Program of Cancer Registries) and SEER (Surveillance, Epidemiology, and End Results) registries.

¹CIR was calculated using the following equation: 1–exp [−Σ_i (IR_i) (Δt_i)]. Where IR_i is age-specific incidence rate and Δt_i indicates the range of each age stratum.

Over a lifetime, younger women with breast cancer were estimated to have more life-years lost with an estimated EYLL of 12.78 years compared with 4.99 years for older women P<0.00025 (Fig. 1a). By racial/ethnic group, younger NHB women had more life-years lost with an estimated EYLL of 15.53 years compared with NHW women, (EYLL = 11.87 years), P <0.00025 (Fig. 1b). Similarly, younger Hispanic women were more likely than NHW women to have greater life-years lost (EYLL = 14.23 vs. 11.87 year) (Fig. 1c).

By stage at diagnosis, the estimated life-years lost for all younger women were EYLL of 8.83, 16.12, and 33.15 years for localized, regional and distant stages compared with estimates for older women of 1.83, 7.76, and 21.51 years for localized, regional and distant stages, P <0.00025 (Table 2). Younger NHB women’s EYLL was 7.89 and 18.42 for localized and regional stages compared with estimates for NHW women, EYLL were 9.30 and 13.95 years for localized and regional stages (P <0.00025). The estimated EYLL was greater for younger Hispanic women than NHW women in regional and distant stages (20.36 and 33.96 years). These estimates indicate that in all stages at diagnosis, younger women have more significant years of life lost than older women. Similarly, younger NHB women experience significantly more years of life lost at regional stage; however at localized stage, younger NHW women have slightly higher years of life lost.

3.2. Estimated CIR_15–44, _45–64 for breast cancer

Overall, the CIR_{15–44,45–64} for younger women during the time period 2009–2013 was estimated to be 0.0109 vs 0.0479 for older women (Table 2). The results imply that among women aged 15–44 years, 1 in 92 will be diagnosed with an invasive breast cancer compared to 1 in 21 for women age 45–64 years. In other words, 1.09% of younger women would develop an invasive breast cancer by age 45 and 4.79% of older women would develop an invasive breast cancer by age 65. By race/ethnicity, the CIR_15–44 estimate for younger NHB women was 0.0116, indicating that 1 in 86 will be diagnosed with an invasive breast cancer compared to 1 in 87 for younger NHW women (CIR_15–44 = 0.0115). For younger Hispanic women, the estimate was 0.0076 or 1 in 132 will be diagnosed with invasive breast cancer by age 45.

3.3. Incidence and mortality rate ratios

Table 3 presents the age-adjusted IRR and MRR among younger NHB-to-NHW women, and younger Hispanic-to-NHW women by breast cancer and all other female cancer sites. Among younger women, the breast cancer incidence rate was 10% higher for NHB than NHW (IRR = 1.10; 95% CI = 1.08–1.11) (Table 3). On the other hand, the incidence rate for all other female cancer sites was significantly lower in NHB compared with NHW women (IRR = 0.70; 95% CI = 0.69–0.70). In general, the racial/ethnic disparity in incidence rate was worse in breast cancer than in all other female cancers. In contrast, the estimated breast cancer incidence rate and the rate for all other female cancers were lower in Hispanic than NHW women (IRR = 0.73; 95% CI = 0.72–0.73 and IRR = 0.73; 95% CI = 0.72–0.73), respectively.

Table 3.

Estimated age-adjusted incidence and mortality rate ratios in breast and all female cancer sites among younger women^a by race/ethnicity, SEER and NPCR, 2009–2013.

	Incidence rate ratios		Mortality rate ratio
	Race/ethnicity by younger women		Race/ethnicity by younger women
	15–44 years NHB: NHW RRb	15–44 years Hispanic: NHW RRc	15–44 years NHB: NHW RRb	15–44 years Hispanic: NHW RRc
	(95% CI)	(95% CI)	(95% CI)	(95% CI)
All other female cancer sites	0.70*	0.73*	1.17*	0.80*
	(0.69–0.70)	(0.72–0.73)	(1.16–1.19)	(0.79–0.81)
Breast	1.10*	0.73*	2.02*	0.78*
	(1.08–1.11)	(0.72–0.75)	(1.94–2.11)	(0.73–0.82)

NHW: Non-Hispanic White; NHB: Non-Hispanic Black; SE, standard error of mean; RR: rate ratio; CI: confidence interval; NOS: not otherwise specified; Rates are per 100,000 and age-adjusted to the 2000 US standard population (19 age groups – Census P25-1130) standard.

^*The rate ratio indicates that the rates are significantly different (P <0.05).

^aYounger women was defined as those aged 15–44 years.

^bThe NHB-to-NHW ratio for younger women was the age-adjusted incidence and mortality rates for NHB women aged 15–44 years divided by the age-adjusted incidence and mortality rates for NHW aged 15–44 years, and age-adjusted incidence and mortality rates obtained from the 2009–2013 NPCR (National Program of Cancer Registries) and SEER (Surveillance, Epidemiology, and End Results) registries.

^cThe Hispanic-to-NHW ratio for younger women was the age-adjusted incidence and mortality rates for Hispanic women aged 15–44 years divided by the age-adjusted incidence and mortality rates for NHW women aged 15–44 years, and age-adjusted incidence and mortality rates obtained from the 2009–2013 NPCR and SEER registries.

The estimated mortality rate for breast cancer was twice as high for younger NHB compared with NHW women (MRR = 2.02; 95% CI = 1.94–2.11). Similarly, the rate for all other female cancer sites was also higher for NHB compared with NHW women (MRR = 1.17; 95% CI = 1.16–1.19). The disparity in mortality rate was worse in breast cancer than in all other female cancers. On the contrary, younger Hispanic women were significantly less likely than NHW women to die of breast cancer (MRR = 0.78; 95% CI = 0.73–0.82). A similar result was also observed in all other female cancers (MRR = 0.80; 95% CI = 0.79–0.81).

4. Discussion

Using multiple measures of population health, there were significant age and racial/ethnic disparities among younger women across five measures of population health. Compared with older women, a significant proportion of younger women have more years of life lost and a greater occurrence of being diagnosed with breast cancer at late stages. However, younger women have a lower risk of developing breast cancer. Further, relative to younger NHW women, a greater proportion of younger NHB women were diagnosed at late stages (i.e., regional and distant), had lower life expectancy, greater years of life lost, a higher probability of being diagnosed with breast cancer at an early age and a greater burden of age-adjusted incidence and mortality rates. Similarly, younger Hispanic women had a high rate of being diagnosed with breast cancer at late-stages, have a high proportion of years of life lost, but have less probability of being diagnosed with breast cancer as well as less likely to die from it compared with NHW women.

The findings from the use of these measures are consistent with previous literature on the age disparity [4–9,32] and is also consistent with previous work on the racial/ethnic disparity and confirms that NHB women experience a higher burden of disease from breast cancer at a younger age [4,10–13,33,34]. To our knowledge, there are no other studies that have quantified the burden of breast cancer in younger vs older women, younger NHB vs NHW women, and younger Hispanic vs NHW women using these multiple measures of health. Prior to this paper, most studies examined racial/ethnic disparities in breast cancer, but they did not make race/ethnic-specific comparisons between younger versus older women [10,11,35].

Currently, there are no studies that have quantified the burden of breast cancer in younger women using EYLL. However, compared with findings from older women, younger women experience greater years of life lost with an additional 7.79-year decrease in life span [24,36]. Consistent with shorter life expectancy observed among younger NHB women, the average years of life lost was greater for NHB and Hispanic than for NHW women, with NHB and Hispanic women experiencing an additional 3.36-year and 2.36-years decrease in life span.

We are not aware of any previously published estimates of CIR_15–44 on breast cancer in younger women, but postulate that these estimates may increase in the future given recent studies reporting the increasing number of new cancer cases and widening disparities [37–41]. The cumulative probability of breast cancer occurrence for women 15–44 years showed that more NHB women and fewer Hispanic than NHW women were diagnosed with an invasive breast cancer by age 45.

Estimates of IRR and MRR revealed significant disparities in incidence and mortality rates for breast cancer and in all other female cancer sites. These findings are consistent with previous reports [22,38–41] and a reminder that regardless of improvement in breast cancer survivorship, racial/ethnic disparities still persistent. The disparities in incidence may reflect the greater decline in incidence for white women than for black women. Among white women, this decline is partly due to decreasing use of hormone replacement therapy (HRT) [42]. Black women did not experience this level of benefit because their use of HRT was low [42]. Further, a recent study has found a convergence of incidence rates between black and white women [43]. As reported in this paper, incidence rates increased from 2009 to 2013 for NHB women, while the rates for NHW women decreased. Further, breast cancer deaths for NHB women are expected to increase, which likely reflects the growing, aging population [44]. Many factors contribute to large mortality gaps. For instance, compared with white women, black women are more likely to be diagnosed at later stage as reported in this paper and less likely to receive timely and high quality treatment at the time of diagnosis [35,45–51]. Further, compared with white women, black women are more likely to have tumor subtypes, especially the triple negative subtype, which have poorer prognosis [52–56]. Unlike younger black women, younger Hispanic women are less likely to be diagnosed and die from breast cancer than non-Hispanic White women. This finding is consistent with previous reports (40,42,60). However, there is a lot of variation within Hispanic subgroups and additional work is needed [57].

As demonstrated in this study, age and racial/ethnic disparities in breast cancer still remain. However, there have been efforts to address age- and racial/ethnic group disparities [58]. For example, the CDC has recently launch a multimedia, multi-pronged national campaign to educate younger women on the risk factors for breast cancer, encourage them to learn their family history of breast cancer, inspire them to talk to their healthcare provider if they think they might be at higher risk, and encourage them to live healthy lifestyles and be aware of their own breast health [59]. Given that these interventions are still in the nascent stages, the findings reported in this paper could be useful to inform decisions to effectively target populations with disproportionate burden of breast cancer. Additionally, the data reported in this paper could be used as inputs to conduct economic studies to evaluate the cost-effectiveness of interventions designed to reduce breast cancer in younger women.

According to the Institute of Medicine, no single measure can sufficiently capture the health of the nation [60]. Therefore, the use of multiple measures of population health to quantify the magnitude of breast cancer disparities provides a more meaningful representation of the burden of breast cancer. Findings reported in each of these measures may be helpful for program planners and decision makers to inform allocation of resources and effectively target subgroups of the population with a disproportionate burden of breast cancer disease. More efforts are needed to detect cancer at an early, treatable stage and to ensure timely access to high quality treatment to reduce this disproportionate burden.

This study has some limitations. First, this study only provides estimates of the average loss of LE by cancer stage and did not consider other factors, such as comorbidity and disability, therefore, reported LE may be overstated [61,62]. Second, calculated CIR_15–44 may be slightly overestimated because the approach assumes that the current risk estimates remain stable during the follow-up period (2009–2013) and the population under study is not subject to competing risk of death from other causes [63]. Finally, given that Hispanics are more likely to have incomplete follow-up for censored cases than whites or blacks in SEER dataset, estimates for Hispanic ethnicity should be interpreted with caution [64]. However, we used the active follow-up (reported alive method) to calculate their survival interval; hence Hispanics’ survival may not be overestimated.

In conclusion, there are substantial disparities in breast cancer between younger compared with older women, and younger NHB women compared with younger NHW women in the multiple measures of population health used in this study. This suggests that many younger women, especially NHB are disproportionately impacted by breast cancer compared to their counterparts. Expanded efforts are needed to understand how to better address these disparities through primary prevention and improve access to quality healthcare.