Inadequate use of screening mammography may be an important reason that African-American women are more likely to be diagnosed with advanced stage breast cancer than members of other ethnic groups, according to a new study led by a University of California, San Francisco imaging specialist.
Results from the six-year study analyzing data from mammograms of 1 million women 40 years of age and over are reported in the April 18 issue of the Annals of Internal Medicine.
Through the 1990s, mortality rates from breast cancer in the United States decreased as the use of mammography increased. These decreases primarily benefited non-Hispanic white women, whereas the mortality rate for African-American women changed very little, according to the research team.
"We found significant differences in the patterns of mammography by race and ethnicity. All minority women were significantly more likely to be inadequately screened with mammography than white women," said Rebecca Smith-Bindman, MD, lead investigator and UCSF associate professor in the departments of radiology, epidemiology and biostatistics, and obstetrics, gynecology and reproductive sciences. "It was important to determine whether the use of mammography was the reason for the racial and ethnic differences in breast cancer. There has been an ongoing debate whether biology, or use of screening mammography, is primarily the cause for the racial and ethnic differences in outcomes."
The researchers linked data from mammography and tumor registries from facilities that form the Breast Cancer Surveillance Consortium funded by the National Cancer Institute. Surveys completed by patients at each mammography examination included questions on race, ethnicity, presence of breast symptoms and previous mammography use.
"We explored stage of disease at diagnosis, tumor characteristics and lymph node involvement among women of different races and ethnicities whose patterns of mammography use were similar," Smith-Bindman said.
The data showed that African-American women are more likely to have large, advanced-stage tumors at diagnosis of breast cancer than white women.
Researchers explored mammography use as a possible cause of the racial and ethnic differences in the rates of advanced cancer. They found that white women were more likely to be screened at an interval of one to two years. Compared with 72 percent of white women, only 63 to 68 percent of African-American, Hispanic, Asian and Native American women were frequently screened. African-American, Hispanic and Asian women were more likely to have never undergone screening; therefore they were more likely to have their first mammogram because of a physical examination finding or breast symptom.
For example, 18 percent of white women with breast cancer were inadequately screened with mammography prior to breast cancer, while 34 percent of African-American, 24 percent of Hispanic and 27 percent of Native American women were inadequately screened before their breast cancer diagnosis.