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Breast cancer mortality rate higher in black women than white women
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Black women were at a nearly 50% increased risk for overall breast cancer-specific mortality than women of other races, according to findings presented at the Fifth AACR Conference on the Science of Cancer Health Disparities.
“This difference was greatest in the first 3 years after diagnosis,” Erica Warner, MPH, ScD, a postdoctoral fellow at Harvard School of Public Health, said in a press release.
The primary aim of the study was to assess links between race/ethnicity and breast cancer-specific survival. Warner and colleagues also sought to investigate whether tumor characteristics, treatment, anthropomorphic and sociodemographic factors mediate disparities.
The study included 19,480 women with stage I to stage III breast cancer who presented to National Comprehensive Cancer Network centers.
Accrual occurred between January 2000 and December 2007. Median follow-up lasted 6.9 years and continued through December 2009.
The study included 634 Asians (defined as non-Hispanic Asian-Pacific Islanders), 1,291 Hispanics, 1,500 non-Hispanic blacks and 16,055 non-Hispanic whites.
The researchers noted non-proportional hazards among black patients. Because of this, analyses for total breast cancer, ER-positive and ER-negative, and basal tumors were performed in two time periods: 0 to 3 years, and 3 years to end of follow-up (EOF).
Multivariate analysis results indicated that blacks had a higher risk for breast cancer-specific death overall (years 0-3: HR=1.48; 95% CI, 1.12-1.94; years 3 to EOF: HR=1.34; 95% CI, 1.06-1.69), as well as among ER-positive 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), luminal B subtypes (HR=1.76; 95% CI, 1.30-2.39) and luminal A subtypes (HR=1.66; 95% CI, 1.03-2.67).
“This finding is important because these are the types of tumors that we traditionally think of as more treatable,” Warner said.
Researchers observed no significant differences between blacks and whites for ER-negative, basal and HER-2 over-expressed tumors after adjustments were made for age, socioeconomic status factors, tumor characteristics and treatment variables.
Results of a fully adjusted model indicated significantly lower risk for breast cancer-specific death among Asians compared with whites (all cancers: HR=0.60; 95% CI, 0.40-0.90; ER-negative tumors: HR=0.51; 95% CI, 0.27-0.94; luminal A: HR=0.23; 95% CI, 0.06-0.93; HER-2 over-expressed tumors: HR=0.25; 95% CI, 0.07-0.92).
The investigators observed no significant differences in breast cancer death between Hispanics and whites.
Tumor markers such as estrogen, progesterone, HER-2/neu and grade mediated the proportion of excess breast cancer mortality among blacks by a proportion of 24.8% (P<.0001). Stage at diagnosis (18.2%, P=.002), comorbidity score (13.8%, P=.02), BMI (9.8%, P=.04) and insurance type (9.5%, P=.04) also mediated breast cancer mortality among blacks.
BMI was observed to be a mediator among Asians (13.9%, P=.06).
“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.”
For more information:
Warner ET. Presented at: The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Oct. 27-30, 2012; San Diego.