Mediation analysis of racial disparities in triple-negative breast cancer incidence among postmenopausal women

Racial disparities in outcomes of patients with stage I-III triple-negative breast cancer after adjuvant chemotherapy: a post-hoc analysis of the E5103 randomized trial

PURPOSE

Breast cancer mortality is higher in Black women than other racial groups. This difference has been partially attributed to a higher proportion of triple-negative breast cancer (TNBC). However, it is uncertain if survival disparities exist in racially diverse TNBC patients receiving similar treatments. Here, we examine racial differences in disease-related outcomes in TNBC patients treated on the E5103 clinical trial.

METHODS

From 2007 to 2011, 4,994 patients with stage I-III HER2-negative breast cancer were randomized to adjuvant chemotherapy with or without bevacizumab. This analysis was limited to the subset of 1,742 TNBC patients with known self-reported race. Unadjusted Kaplan-Meier curves and adjusted Cox-Proportional Hazards models were used to determine breast cancer events and survival outcomes.

RESULTS

Of the analysis population, 51 (2.9%) were Asian, 269 (15.4%) Black, and 1422 (81.6%) White. Median age was 51 years. Patient characteristics, treatment arm, and local therapies were similar across racial groups. White women were more commonly node-negative (56% vs. 49% and 44% in Asian and Black women, respectively; p < 0.01). At a median follow-up of 46 months, unadjusted Kaplan-Meier locoregional and distant recurrence, and disease-free and overall survival, did not differ significantly by race. In Cox models adjusted for patient and tumor characteristics and treatment arm, race was not associated with any disease event. Larger tumor size and nodal involvement were consistently associated with breast cancer events.

CONCLUSION

This clinical trial population of similarly treated TNBC patients showed no racial differences in breast cancer outcomes. Disease extent, rather than race, was associated with disease events.

Neighborhood factors and triple negative breast cancer: The role of cumulative exposure to area-level risk factors

BACKGROUND

Despite similar incidence rates among Black and White women, breast cancer mortality rates are 40% higher among Black women. More than half of the racial difference in breast cancer mortality can be attributed to triple negative breast cancer (TNBC), an aggressive subtype of invasive breast cancer that disproportionately affects Black women. Recent research has implicated neighborhood conditions in the etiology of TNBC. This study investigated the relationship between cumulative neighborhood-level exposures and TNBC risk.

METHODS

This single-institution retrospective study was conducted on a cohort of 3316 breast cancer cases from New Castle County, Delaware (from 2012 to 2020), an area of the country with elevated TNBC rates. Cases were stratified into TNBC and "Non-TNBC" diagnosis and geocoded by residential address. Neighborhood exposures included census tract-level measures of unhealthy alcohol use, metabolic dysfunction, breastfeeding, and environmental hazards. An overall cumulative risk score was calculated based on tract-level exposures.

RESULTS

Univariate analyses showed each tract-level exposure was associated with greater TNBC odds. In multivariate analyses that controlled for patient-level race and age, tract-level exposures were not associated with TNBC odds. However, in a second multivariate model that included patient-level variables and considered tract-level risk factors as a cumulative exposure risk score, each one unit increase in cumulative exposure was significantly associated with a 10% increase in TNBC odds. Higher cumulative exposure risk scores were found in census tracts with relatively high proportions of Black residents.

CONCLUSIONS

Cumulative exposure to neighborhood-level risk factors that disproportionately affect Black communities was associated with greater TNBC risk.

Racial differences in anthropometric measures as risk factors for triple-negative breast cancer

PURPOSE

The incidence of triple-negative breast cancer (TNBC) is higher in Black women compared to White women which is not explained by racial differences in body mass index (BMI). As BMI has limitations as an anthropometric measure, we used different anthropometric measures to examine associations with TNBC by race.

METHOD

Of 161,808 postmenopausal participants in Women's Health Initiative, eligible were a subsample of 121,744 White and Black postmenopausal women enrolled from 1993 to 1998, 50-79 years of age with anthropometric measures who were followed for breast cancer incidence until March 2019. At entry, BMI, waist circumference (WC), and waist-hip ratio (WHR) were measured using standardized methods. Breast cancers were verified by central medical record review. Associations between anthropometric measures and triple-negative breast cancer risk were examined using Cox proportional hazards regression models.

RESULTS

After 17.6 years (median) follow-up, there were 87 Black women and 529 White women with incident triple-negative breast cancer. Overall, there were no significant associations between anthropometric measures and risk of triple-negative breast cancer. However, compared to White women with normal BMI, White women with obesity (BMI ≥ 30) (HR 0.76, 95% CI 0.60, 0.96) were significantly associated with a lower risk of triple-negative breast cancer. And larger waist circumference (HR per centimeter 0.99, 95% CI 0.99, 1.00) was significantly associated with a lower risk of triple-negative breast cancer among White women.

CONCLUSION

Overall, among postmenopausal women, anthropometric measures were not associated with risk of TNBC. The association among White women with larger waist circumference and women with obesity with a lower risk of triple-negative breast cancer needs further confirmation.

Development and validation of nomograms for predicting survival in patients with de novo metastatic triple-negative breast cancer

Metastatic triple-negative breast cancer (mTNBC) is a heterogeneous disease with a poor prognosis. Individualized survival prediction tool is useful for this population. We constructed the predicted nomograms for breast cancer-specific survival (BCSS) and overall survival (OS) using the data identified from the Surveillance, Epidemiology, and End Results database. The Concordance index (C-index), the area under the time-dependent receiver operating characteristic curve (AUC) and the calibration curves were used for the discrimination and calibration of the nomograms in the training and validation cohorts, respectively. 1962 mTNBC patients with a median follow-up was 13 months (interquartile range, 6–22 months), 1639 (83.54%) cases died of any cause, and 1469 (74.87%) died of breast cancer. Nine and ten independent prognostic factors for BCSS and OS were identified and integrated to construct the nomograms, respectively. The C-indexes of the nomogram for BCSS and OS were 0.694 (95% CI 0.676–0.712) and 0.699 (95% CI 0.679–0.715) in the training cohort, and 0.699 (95% CI 0.686–0.712) and 0.697 (95% CI 0.679–0.715) in the validation cohort, respectively. The AUC values of the nomograms to predict 1-, 2-, and 3-year BCSS and OS indicated good specificity and sensitivity in internal and external validation. The calibration curves showed a favorable consistency between the actual and the predicted survival in the training and validation cohorts. These nomograms based on clinicopathological factors and treatment could reliably predict the survival of mTNBC patient. This may be a useful tool for individualized healthcare decision-making.

Racial disparities in triple negative breast cancer: toward a causal architecture approach

BACKGROUND

Triple negative breast cancer (TNBC) is an aggressive subtype of invasive breast cancer that disproportionately affects Black women and contributes to racial disparities in breast cancer mortality. Prior research has suggested that neighborhood effects may contribute to this disparity beyond individual risk factors.

METHODS

The sample included a cohort of 3316 breast cancer cases diagnosed between 2012 and 2020 in New Castle County, Delaware, a geographic region of the US with elevated rates of TNBC. Multilevel methods and geospatial mapping evaluated whether the race, income, and race/income versions of the neighborhood Index of Concentration at the Extremes (ICE) metric could efficiently identify census tracts (CT) with higher odds of TNBC relative to other forms of invasive breast cancer. Odds ratios (OR) and 95% confidence intervals (CI) were reported; p-values < 0.05 were significant. Additional analyses examined area-level differences in exposure to metabolic risk factors, including unhealthy alcohol use and obesity.

RESULTS

The ICE-Race, -Income-, and Race/Income metrics were each associated with greater census tract odds of TNBC on a bivariate basis. However, only ICE-Race was significantly associated with higher odds of TNBC after adjustment for patient-level age and race (most disadvantaged CT: OR = 2.09; 95% CI 1.40-3.13), providing support for neighborhood effects. Higher counts of alcohol and fast-food retailers, and correspondingly higher rates of unhealthy alcohol use and obesity, were observed in CTs that were classified into the most disadvantaged ICE-Race quintile and had the highest odds of TNBC.

CONCLUSION

The use of ICE can facilitate the monitoring of cancer inequities and advance the study of racial disparities in breast cancer.

A Population Health Assessment in a Community Cancer Center Catchment Area: Triple negative breast cancer, alcohol use, and obesity in New Castle County, Delaware

BACKGROUND

The National Cancer Institute (NCI) requires designated cancer centers to conduct catchment area assessments to guide cancer control and prevention efforts designed to reduce the local cancer burden. We extended and adapted this approach to a community cancer center catchment area with elevated rates of triple negative breast cancer (TNBC).

METHODS

Cancer registry data for 462 TNBC and 2,987 Not-TNBC cases diagnosed between 2012 and 2020 at the Helen F. Graham Cancer Center & Research Institute (HFGCCRI), located in New Castle County, Delaware, were geocoded to detect areas of elevated risk ('hot spots') and decreased risk ('cold spots'). Next, electronic health record (EHR) data on obesity and alcohol use disorder (AUD) and catchment-area measures of fast-food and alcohol retailers were used to assess for spatial relationships between TNBC hot spots and potentially modifiable risk factors.

RESULTS

Two hot and two cold spots were identified for TNBC within the catchment area. The hot spots accounted for 11% of the catchment area but nearly a third of all TNBC cases. Higher rates of unhealthy alcohol use and obesity were observed within the hot spots.

CONCLUSIONS

The use of spatial methods to analyze cancer registry and other secondary data sources can inform cancer control and prevention efforts within community cancer center catchment areas, where limited resources can preclude the collection of new primary data.

IMPACT

Targeting community outreach and engagement activities to TNBC hot spots offers the potential to reduce the population-level burden of cancer efficiently and equitably.

Local treatment for triple-negative breast cancer patients undergoing chemotherapy: breast-conserving surgery or total mastectomy?

Background

Because there is no exact therapeutic target, the systemic treatment of triple-negative breast cancer (TNBC) still relies on chemotherapy. In terms of local treatment, based on the highly malignant characteristics of TNBC, it is still uncertain whether patients should be given more aggressive local treatment.

Methods

This study was based on the SEER database. 13,262 TNBC patients undergoing chemotherapy were included. According to local treatment methods, patients were divided into breast-conserving surgery with radiotherapy (BCS + RT), total mastectomy alone and total mastectomy with radiotherapy (Mastectomy+RT). Kaplan-Meier survival analysis drew the survival curves of Overall Survival (OS) and Breast Cancer Specific Survival (BCSS), and Cox proportional risk regression models were used to analyze the impact of different local treatments on OS and BCSS.

Results

After adjusting confounding factors, Mastectomy alone group (HR = 1.57; 95%CI: 1.40–1.77) and Mastectomy+RT group (HR = 1.28; 95%CI: 1.12–1.46) were worse in OS than BCS + RT group, and Mastectomy+RT group (HR = 0.81; 95%CI: 0.73–0.91) was better in OS than Mastectomy alone group. The effect of local treatment for BCSS was similar to that of OS. After stratification according to age, tumor size and lymph node status, when the age was less than 55 years old, at T4, N2 or N3 category, there was no statistical significance between the BCS + RT group and the Mastectomy+RT group in OS or BCSS (all P > 0.05). When the age was less than 65 years old, at T1, T2 or N0 category, there was no statistical significance between the Mastectomy alone group and the Mastectomy+RT group in OS or BCSS (all P > 0.05). The results of other stratified analyses were basically consistent with the results of total population analysis.

Conclusion

The survival benefit of breast-conserving surgery with radiotherapy was higher than or similar to that of total mastectomy TNBC patients.