NEW YORK -- As breast cancer diagnosis and treatment options grow more complex, race plays a larger role in survival, researchers here reported.
NEW YORK, Aug. 13 -- As breast cancer diagnosis and treatment options grow more complex, race plays a larger role in survival, researchers here reported.
After adjusting for tumor size and lymph node status as well age and other factors, the mortality rate for African-American women with breast cancer was as much as 56% higher than that for whites, Alfred I. Neugut, M.D., Ph.D., of Columbia University, and colleagues reported in the Sept. 15 issue of Cancer.
Black women have higher breast cancer mortality rates, are more likely to be diagnosed at an advanced stage of the disease, and have worse stage-for-stage survival than white women, the researchers said.
Whether these disparities are caused by a difference between races in tumor biology or to nonclinical socioeconomic factors that affect access to care has been unclear, Dr. Neugut said.
At the outset, the researchers had hypothesized that within-stage differences in tumor size and number of positive lymph nodes between blacks and whites might account for some of the observed stage-for-stage disparities in survival. However, this turned out not to be so, they said.
The findings came from analysis of information on 256,174 women with breast cancer contained in the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database. The women were diagnosed with a first primary tumor (TNM stage I-IIIA breast cancer) from 1988 through 2003.
There were 21,861 black women among the SEER cases and 234,313 white women.
Among those with lymph node-negative breast cancer more black women had tumors measuring ?2.0 cm at diagnosis than white women had.
Blacks were also 24% more likely than whites to have one or more positive lymph nodes (odds ratio [OR], 1.24; 95% confidence interval 1.20-1.28), adjusting for tumor size.
And, after adjusting for tumor size, age, and TNM stage, African-American women were more likely than white women to die from the disease. The adjusted mortality rate ratio for blacks versus whites was 1.56 (CI, 1.51-1.61).
Adjustment for within-stage differences in tumor size and lymph node involvement were found to be negligible and did not appear to reduce the racial disparity, the researchers said.
Even after controlling for known clinical and biologic factors that affect prognosis, black women still had a 39% higher mortality rate (rate ratio 1.39 (CI, 1.35-1.44).
A "new interesting" finding was the statistically significant interaction between race and stage of disease at diagnosis with respect to mortality, the researchers said.
Significantly, the rate ratio reflecting racial disparity increased as the stage of disease increased.
One plausible explanation, they suggested, is that when breast cancer is diagnosed at a more advanced stage, curative surgery is more complex, requiring more extensive surgery, as well as a need for radiation and chemotherapy.
Studies have suggested that the disparity noted in breast cancer survival is related to differences in the quality of adjuvant treatment, delayed start of adjuvant therapy, completion of the treatment regimen, and adherence, the authors noted.
An earlier study reported by these researchers found that a substantial fraction of women with early-stage breast cancer received less than 75% of their chemotherapy regimen and that early termination was associated with both black race and poorer overall survival.
Noting the limitations of the current study, the researchers said that most stemmed from the limited range of data available from the SEER registry.
Specifically, the study could not account for differences in treatment, obesity, and other comorbid conditions, which are more likely among blacks.
The low level of information about socioeconomic status in this population also limited the ability to understand its role in breast cancer survival.
Socioeconomic status is of particular concern when considering the frequency with which multiple risk factors including decreased access to screening and treatment, comorbid conditions, and a greater likelihood of biologically unfavorable tumor characteristics are often clustered in economically and socially deprived individuals, the researchers said.
Adjusting for within-stage differences in tumor size and lymph node status, the original hypothesis, did not appear to reduce the racial disparity, the researchers said.
However, the finding that the disparity in racial survival increased with greater stage of disease at diagnosis was unexpected, Dr. Neugut said. "If this latter finding is confirmed, efforts aimed at reducing racial disparities should focus on eliminating barriers to quality care in black women with higher-stage disease," he concluded.
This study was supported by an R25 Award from the National Cancer Institute and a T32 Award from a grant from the National Center for Research Resources of the National Institutes of Health; a K07 Award from the NCI; a K05 Award from the NCI; a grant from the American Cancer Society; and a grant from the Department of Defense.