February 04, 2015
2 min read

Breast cancer stage at diagnosis, survival vary by race, ethnicity

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The likelihood that women with invasive breast cancer will be diagnosed at an early stage, as well as survival outcomes for those diagnosed with stage I disease, varied considerably by race and ethnicity, according to an observational study.

Black women were less likely to be diagnosed with stage I breast cancer than non-Hispanic white women, results showed. Among women with small tumors, blacks were twice as likely to die of breast cancer than non-Hispanic whites.

Steven A. Narod, MD, FRCPC

Steven A. Narod

Factors such as socioeconomic status, access to and use of health care, treatment adherence and comorbidities may contribute to the disparities, according to researchers. However, they determined much of the difference can be explained by intrinsic biological differences, such as triple-negative behavior, lymph node or distant metastasis.

“There are disparities in access to care and in the level of awareness regarding early diagnosis in the United States,” Steven A. Narod, MD, FRCPC, senior scientist at the Women’s College Research Institute at Women’s College Hospital in Toronto, told HemOnc Today. “It is laudable that we should strive to eliminate these disparities, but our [study] suggests that even if access to care was ideal for all women in the United States, there would remain some differences in the outcomes of breast cancer patients, attributable to inherent factors.”

Narod and colleagues used the SEER 18 registries database — which accounts for about 28% of the US population — to conduct an observational study of women diagnosed with invasive breast cancer between 2004 and 2011.

The investigators looked at the stage of breast cancer at the time of diagnosis and the 7-year breast cancer-specific survival, adjusted for age at diagnosis, income and ER status.

Of the 373,563 women studied, 71.9% were non-Hispanic white, 9.4% were Hispanic-white, 10.4% were black, 6.7% were Asian and 1.6% were other ethnicities.

Results showed black women were less likely to be diagnosed with stage I breast cancer than non-Hispanic white women (37% vs. 50.8%).

Multivariable analysis, performed after a mean follow-up of 40.6 months (median, 38 months), showed the 7-year actuarial risk for death from stage I breast cancer was significantly higher for black women compared with non-Hispanic white women (6.2% vs. 3%; HR=1.57; 95% CI, 1.4-1.75).

In a subgroup of women with breast cancer tumors that were ≤2 cm, black women were significantly more likely to die of breast cancer than non-Hispanic white women (9% vs. 4.6%; HR=1.96; 95% CI, 1.82-2.12). That higher risk persisted when the model was adjusted for age, income and ER status (HR=1.56; 95% CI, 1.45-1.69).

“Beyond screening and treatment differences, failures in the delivery and development of novel interventions must be addressed,” Bobby Daly, MD, and Olufunmilayo I. Olopade, MBBS, FACP, both of the University of Chicago Medical Center, wrote in an accompanying editorial. “The study … demonstrates likely intrinsic differences in the aggressiveness of the tumors between black and white patients. … Thus, there is evidence of a high rate of inherited mutations in genes that might explain increased risk for young-onset aggressive breast cancers in women.” – By Anthony SanFilippo

Disclosure: The researchers report no relevant financial disclosures.

Steven A. Narod, MD, FRCPC, can be reached at Women’s College Research Institute, 790 Bay Street, 7th Floor, Toronto, Ontario, Canada M5G 1N8; email: steven.narod@wchospital.ca.