A new report shows that the number of black women who are diagnosed with breast cancer is on the rise, but doctors are not sure what is causing the increased numbers.
About 232,000 women will be diagnosed with breast cancer in 2013, according to government statistics. More than 39,000 women are expected to die from the disease this year.
About eight in 10 breast cancer cases and almost nine in 10 breast cancer deaths occur in women 50 years of age and older.
Previous research suggests black women with the disease fare worse than diagnosed white women.
A Harvard study presented at the American Association for Cancer Research medical conference in Oct. 2012 found within three years of a breast cancer diagnosis,.
This June, a JAMA study showed thatbecause they undergo fewer screenings, have poorer health at the time of diagnosis and have more advanced disease by the time the cancer is found.
The new report, published Oct. 1 in the American Cancer Society's journal CA: A Cancer Journal for Clinicians, tracked breast cancer incidence and death rates from 2006 through 2010.
White women historically have had the highest breast cancer rates among women over 40, according to the authors, but black women are closing the gap, especially those 50 to 59 years old.
Black women saw a 0.2 percent increase in breast cancer rates during the five-year study period, while there was no change among white, Asian and American Indian women. Hispanic women saw a 0.6 percent drop in breast cancer rates.
Black women continue to be more likely than other women to be diagnosed with breast cancer before age 40, and were more likely to die of breast cancer at any age compared to other women.
The new report found breast cancer death rates have dropped 34 percent since 1990.
"Although the incidence haven't declined, we have made strides in the effort to improve the survival rate," Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, told HealthDay.
"However, not all ethnic groups are enjoying this improved survival," added Bernik, who was not involved in the research.
The report also broke down the types of breast cancer women were getting. For all age groups, white women have the highest rates of ER-positive (meaning they respond to estrogen) breast cancers, and black women have the highest rates of ER-negative breast cancer.
These trends may reflect racial differences in disease risk factors. The authors said reproductive history and obesity are more strongly linked to ER-positive breast cancer, while lower socioeconomic status has been linked to raised risk for ER-negative breast cancer.
The American Cancer Society's full Breast Cancer Facts & Figures 2013-2014 report can be access here.