Public Release:  Increased risk for breast cancer death among black women greatest during first 3 years postdiagnosis

American Association for Cancer Research

SAN DIEGO -- Non-Hispanic black women diagnosed with breast cancer, specifically those with estrogen receptor-positive tumors, are at a significantly increased risk for breast cancer death compared with non-Hispanic white women.

"This difference was greatest in the first three years after diagnosis," said Erica Warner, M.P.H., Sc.D., a postdoctoral fellow at Harvard School of Public Health in Boston, Mass., who presented the data at the Fifth AACR Conference on The Science of Cancer Health Disparities, held here Oct. 27-30, 2012.

Prior research has shown that non-Hispanic black women have lower breast cancer survival rates relative to other racial/ethnic groups.

Warner and colleagues conducted a study of 19,480 women who presented to National Comprehensive Cancer Network centers with stage 1 to stage 3 breast cancer between January 2000 and December 2007. They compared breast cancer-specific mortality among 634 Asian women, 1,291 Hispanic women, 1,500 non-Hispanic black women and 16,055 non-Hispanic white women.

After a median follow-up of 6.9 years, the researchers found that non-Hispanic black women had a 48 percent higher risk for breast cancer death in the first three years after diagnosis compared with non-Hispanic white women. After three years, non-Hispanic black women had a 34 percent increased risk for breast cancer-specific mortality.

"The higher risk for early death among black women was more striking among women with estrogen receptor-positive tumors," Warner said.

Non-Hispanic black women with estrogen receptor-positive tumors were more than twice as likely to die from breast cancer within the first three years of diagnosis compared with non-Hispanic white women. This risk was also increased in non-Hispanic black women with luminal A and luminal B breast cancer subtypes.

"This finding is important because these are the types of tumors that we traditionally think of as more treatable," Warner said.

No difference in breast cancer mortality between non-Hispanic black and white women was found for estrogen receptor-negative, basal or HER2-overexpressing tumor subtypes.

Warner and colleagues also evaluated breast cancer survival among Asian and Hispanic women. Compared with non-Hispanic white women, data indicated that Asian women had a 40 percent lower risk for breast cancer death. The researchers observed this decreased risk in all breast cancers and in estrogen receptor-negative, luminal A and HER2-overexpressing tumors. They found no significant differences between non-Hispanic white women and Hispanic women for breast cancer mortality.

"The results of this study emphasize that clinical management and follow-up for patients with breast cancer, particularly black women, is important in the first few years after diagnosis," Warner said. "Although the difference between blacks and whites was highest for this time period, the risk for death was highest in the first few years after diagnosis for all groups."

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Racial/ethnic differences in breast cancer survival and mediating effects of tumor characteristics, sociodemographic and treatment factors. Erica T. Warner1, Rulla M. Tamimi2, Melissa E. Hughes3, Rebecca A. Ottesen4, Yu-Ning Wong5, Stephen B. Edge6, Richard L. Theriault7, Douglas W. Blayney8, Joyce C. Niland4, Eric P. Winer3, Jane C. Weeks3, Ann H. Partridge3. 1Harvard School of Public Health, Boston, MA, 2Channing Laboratory, Brigham and Women's Hospital, Boston, MA, 3Dana-Farber Cancer Institute, Boston, MA, 4City of Hope Comprehensive Cancer Center, Duarte, CA, 5Fox Chase Cancer Center, Philadelphia, PA, 6Roswell Park Cancer Insitute, Buffalo, NY, 7University of Texas M.D. Anderson Cancer Center, Houston, Texas, 8Stanford University Cancer Center, Palo Alto, CA.

Purpose: To evaluate the relationship between race/ethnicity and breast cancer specific survival and to investigate the mediating effects of tumor characteristics, treatment, anthropomorphic and sociodemographic factors on racial/ethnic disparities in survival.

Methods: Analysis included 19,480 women presenting to National Comprehensive Cancer Network centers with stage I-III breast cancer between January 2000 and December 2007 with National Death Index survival follow-up through December 2009. Multiple Cox proportional hazards regression models were used to compare breast cancer specific mortality by Non-Hispanic Asian-Pacific Islanders (Asian, n=634), Hispanics (Hispanic, n=1,291), Non-Hispanic Blacks (Black, n=1,500) as compared to Non-Hispanic Whites (White, n=16,055) respectively. Additionally models were analyzed overall and also stratified by tumor subtypes. Cox models were analyzed with control variables in steps: age adjusted, plus SES factors, plus tumor characteristics, plus treatment variables. Mediation analyses were performed to estimate the proportion of excess breast cancer mortality mediated through exposures.

Results: Median follow-up time was 6.9 years. Due to non-proportional hazards among Blacks, overall and within certain clinical subgroup models, analyses for total breast cancer, estrogen receptor positive and negative (ER+ and ER-) and basal tumors were performed in two time periods (0-3 years and 3 years to end of follow-up (EOF)). In multivariable fully adjusted models, Blacks had higher risk of breast cancer specific death overall (years 0-3: hazard ratio [HR] 1.48, 95% confidence interval [CI] 1.12-1.94; years 3 to EOF: HR 1.34, 95% CI 1.06-1.69), among ER+ tumors (years 0-3: HR 2.85, 95% CI 1.75-4.62; years 3 to EOF: HR 1.49, 95% CI 1.11-2.00), and for luminal B subtypes (HR 1.76, 95% CI 1.30-2.39) as well as for luminal A subtypes (HR 1.66, 95% CI 1.03-2.67) subtypes. After adjustment for age, SES factors, tumor characteristics and treatment variables there were no significant differences between Blacks and Whites for ER-, basal, or Her2 over expressed tumors. In fully adjusted models Asians were at significantly lower risk of death from breast cancer as compared to Whites (all cancers: HR 0.60, 95% CI 0.40-0.90; ER- tumors: HR 0.51, 95% CI 0.27-0.94; luminal A: HR 0.23, 95% CI 0.06-0.93; HER2 over expressed tumors: HR 0.25, 95% CI 0.07-0.92). There were no significant differences in breast cancer mortality between Hispanics and Whites. The estimated proportion of excess breast cancer mortality among Blacks that was mediated by tumor markers (estrogen, progesterone, and her2neu) and grade was 24.8% (p<0.0001). Other mediators included stage at diagnosis (18.2%, p=0.002), comorbidity score (13.8%, p=0.02), body mass index (BMI) (9.8%, p=0.04), and insurance type (9.5%, p=0.04). Among Asians, BMI (13.9%, p=0.06) was an important mediator. Conclusions: Blacks are at higher risk of breast cancer death as compared to Whites, particularly in the first three years after diagnosis and predominantly among ER+, luminal A and luminal B tumor subtypes. This excess risk is mediated through differences in tumor characteristics, stage at diagnosis, comorbid conditions, BMI, and insurance type. Asian women have better breast cancer survival than Whites somewhat mediated through their lower BMI at diagnosis.

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