Although survival rates with breast cancer have increased overall in recent years, African-American women still tend to have more advanced disease when the diagnosis is made, and to fare less well, than white women. Now, new findings suggest that some of that difference may be because of varying mammography-screening intervals.

Dr. Rebecca Smith-Bindman of the University of California in San Francisco and colleagues examined patterns of mammography using data from the Breast Cancer Surveillance Consortium, and linked this information to tumor registries.

The data covered more than one million women who had undergone mammography at least once between 1996 and 2002. A total of 17,558 women received a first-time diagnosis of breast cancer, the team reports in the Annals of Internal Medicine.

Advanced stage tumors were more frequent in African-American and Hispanic women than whites upon diagnosis, and high-grade tumors were more likely in African-American, Hispanic, and Native American women, the investigators found.

The number of large tumors detected was 1.8 per 1000 mammograms when performed at 1-year intervals, but this rate increased to 4.8 per 1000 when intervals were 4 years or more. White women were more likely than members of other ethnic groups to be screened every year or two.

When the researchers grouped the women according to their screening history, the differences in advanced cancer rates between African-American and white women were diminished or eliminated.

Regardless of ethnicity, “increased adherence to recommended mammography screening intervals… may result in decreased mortality rates,” Smith-Bindman and her colleagues observe.