While breast cancer remains the second leading cause of cancer death among women in the United States, overall mortality rates from the disease have been declining, according to a new report from the American Cancer Society.
Between 1989 and 2015, breast cancer mortality rates decreased by 39%, which extrapolates to about 322,600 deaths that were averted during that period. The death rate continues to be higher among black women than white women nationally, but several states have reported breast cancer mortality that is statistically equivalent between races.
"A large body of research suggests that the black-white breast cancer disparity results from a complex interaction of biologic and nonbiologic factors, including differences in stage at diagnosis, tumor characteristics, obesity, other health issues, as well as tumor characteristics, particularly a higher rate of triple-negative cancer" said lead author, Carol DeSantis, MPH, from Surveillance and Health Services Research at the American Cancer Society.
"But the substantial geographic variation in breast cancer death rates confirms the role of social and structural factors, and the closing disparity in several states indicates that increasing access to health care to low-income populations can further progress the elimination of breast cancer disparities," she said in a release.
These findings come from Breast Cancer Statistics, which is compiled every 2 years by the American Cancer Society and describes the latest trends in breast cancer incidence, mortality, survival, and screening by race/ethnicity and state variations.
The results have been published in CA: A Cancer Journal for Clinicians.
Fewer Deaths Now, but Still Most Common Cancer in US Women
Breast cancer mortality rates had been increasing by 0.4% per year from 1975 to 1989 but since then have been declining, a change attributed to improvements in both treatment and detection. Even so, about 40,610 women residing in the United States are expected to die of this disease in 2017.
The authors note that about 252,710 new cases are expected to be diagnosed in 2017, making breast cancer the most common malignancy diagnosed among US women. Most diagnoses (81%) are in women aged 50 years and older, as are most (89%) breast cancer deaths. The median age at breast cancer death is 68 years overall (70 years for white women and 62 years for black women).
Incidence Increasing in Some Groups
However, while mortality rates have been declining, incidence rates have been climbing in some populations.
Overall breast cancer incidence rates increased between 2004 to 2015 among certain ethnic groups, including Asian/Pacific Islanders (1.7% per year), non-Hispanic blacks (NHBs) (0.4% per year), and Hispanics (0.3% per year) but remained stable among non-Hispanic whites (NHWs) and American Indian/Alaska Natives (AI/ANs).
The trends of rising incidence appear to be driven by increasing rates of hormone receptor–positive breast cancer, which rose among all groups. Conversely, rates of hormone receptor–negative breast cancers declined.
Disparities Remain
The authors note that during the study period, mortality rates declined for all racial/ethnic groups. From 2006 through 2015, annual breast cancer–related death rates dropped 2.6% in AI/ANs, 1.8% in NHWs, 1.5% in NHBs, 1.4% in Hispanics, and 0.9% in APIs.
But while mortality has declined, NHB women continue have higher death rates than NHW women. This rate was 39% higher (mortality rate ratio [MRR], 1.39; 95% confidence interval [CI], 1.35 - 1.43) for NHB women in 2015, but the disparity has not expanded since 2011.
For both black and white women, significant survival gains were made for the various disease stages, with the improvement observed for those with regional-stage disease; survival increased from 68% to 89% for white women and from 55% to 81% for black women.
White women had larger gains for distant-stage disease survival (19% to 37%) vs black women (16% to 26%). These improvements, note the authors, again reflect improved treatment but also decreases in tumor size within each stage of disease.
Breast cancer death rates were higher in NHB women than in NHW women in every state. When the researchers looked at disparities by individual states, there were pronounced regional differences. Excess death rates for black women ranged from 20% in Nevada (MRR, 1.20; 95% CI, 1.01 - 1.42) to 66% in Louisiana (MRR, 1.66; 95% CI, 1.54 - 1.79).
But of note, breast cancer death rates were not statistically different between NHB and NHW women in seven states, which could reflect a closing gap between races or a lack of statistical power due to small numbers of breast cancer deaths among black women.
The authors have disclosed no relevant financial relationships.
CA Cancer J Clin. Published online October 3, 2017. Abstract
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