Stage I Breast Cancer Diagnosis, Risk of Death Varies by Race, Ethnicity

Analysis of records from the US Surveillance, Epidemiology, and End Results 18 database reveals diagnosis and survival disparities by race and ethnicity in invasive breast cancer

medwireNews: Race and ethnicity influence not only the probability of diagnosis at an early stage, but also survival after diagnosis in women with invasive breast cancer, research shows.

Black women were significantly less likely to be diagnosed with stage I breast cancer and had a higher risk of death within 7 years of diagnosis than non-Hispanic White women, report Steven Narod, from Women’s College Hospital in Toronto, Ontario, Canada, and co-workers.

Of the 373,563 women with histologically confirmed invasive breast cancer identified from the US Surveillance, Epidemiology, and End Results (SEER) 18 registries database, the majority were non-Hispanic White (71.9%), Black (10.4%) or Hispanic White (9.4%). The remaining women were Chinese (1.3%), Japanese (1.0%), south Asian (0.6%), other Asian (3.8%) or another ethnicity (1.6%).

The probability of early diagnosis was significantly higher for Japanese than for non-Hispanic White women, with 56.1% versus 50.8% of women being diagnosed at stage I.

By contrast, 37.0%, 40.1% and 40.4% of Black, Hispanic White and south Asian women were diagnosed with stage I breast cancer, respectively – all three rates were significantly lower than that of non-Hispanic White women.

Multivariable analysis showed that these differences remained after adjusting for age, yearly income, Oestrogen receptor stage and race/ethnicity, with Japanese, Black, Hispanic White and south Asian women having an odds ratio of 1.23, 0.65, 0.71 and 0.73, respectively, of a stage I diagnosis compared with non-Hispanic White patients.

The 7-year actuarial risk of mortality due to stage I breast cancer was significantly higher for Black and significantly lower for Asian women compared with White (non-Hispanic and Hispanic) women, with rates of 6.2% and 1.9% versus 3.0%, giving hazard ratios (HRs) of 1.57 and 0.60, respectively.

Black women with small-sized tumours (≤2.0 cm at diagnosis) had a significantly higher likelihood of presenting with lymph node (24.1 vs 18.4%) or distant (1.5 vs 1.0%) metastases than non-Hispanic White women, and were also more likely to die as a result of small-sized tumours, with a statistically significant HR of 1.56.

Additionally, Black women had the highest proportion of triple-negative breast cancers.

These findings led the researchers to conclude in JAMA that much of the observed disparities could be accounted for by intrinsic biological differences.

In an accompanying editorial, Bobby Daly and Olufunmilayo Olopade, from the University of Chicago in Illinois, USA, observe that biology alone is not responsible for the survival disparity in breast cancer and say that other factors, such as quality of breast cancer screening and variations in patterns of care, also contribute to the poorer outcomes for Black women.

They conclude: “Closing the survival gap will only occur once health care leaders initiate system changes that improve access to high-quality care along with a more comprehensive study of breast cancer biology through inclusion of a substantial number of minority patients in ‘omics’ research and in clinical trials.”

References

Iqbal J, Ginsburg O, Rochon PA,et al.Differences in Breast Cancer Stage at Diagnosis and Cancer-Specific Survival by Race and Ethnicity in the United States. JAMA 2015;313: 165–173. doi:10.1001/jama.2014.17322

Daly B, Olopade OI. Race, Ethnicity, and the Diagnosis of Breast Cancer. JAMA 2015;313: 141–142. doi:10.1001/jama.2014.17323

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