Study highlights racial inequalities in mammography screening

April 25, 2006

Both good news and bad news emerged from a million-women-strong trial about race and mammography. On the bright side, mammography screening works across racial and ethnic groups. The bad news is that African American women are less likely to get that screening, possibly explaining their relatively poor mortality rates.

Both good news and bad news emerged from a million-women-strong trial about race and mammography. On the bright side, mammography screening works across racial and ethnic groups. The bad news is that African American women are less likely to get that screening, possibly explaining their relatively poor mortality rates.

In comparison with other racial and ethnic groups, African American women diagnosed with breast cancer are more likely to have large, aggressive tumors that have spread to lymph nodes, according to the prospective study from the University of California, San Francisco.

This finding is based on experience with over one million women seen between 1996 and 2002 as part of the government-funded national Breast Cancer Surveillance Program. Study results were published in the Annals of Internal Medicine in mid-April.

A much-lauded mortality reduction in women with breast cancer has been attributed equally to mammography and treatment. The benefits do not apply to all women, however. Research has shown that mortality rates are significantly worse for African American women. Yet high-profile studies based on patient surveys indicated that women of all races were undergoing mammography at roughly comparable rates.

"White women have seen a benefit in mortality rates, but there has been little change for African American women. We asked, 'Is the persistent difference due to treatment or to mammography?'" said lead investigator Dr. Rebecca Smith-Bindman, a radiologist.

The UCSF study found that 34% of African American women with breast cancer had not had been adequately screened prior to diagnosis, compared with 18% of the affected white women. Nonwhite patients, including African Americans, Latinas, and Asian women, were also more likely to have never had a mammogram.

"Radiologists should welcome the finding that mammography makes a difference. We just need to screen more patients," Smith-Bindman said in an interview with Diagnostic Imaging.

It's possible that previous studies showing comparable access to mammography were overly reliant on patients' self-reporting of their experience. Smith-Bindman pointed out that self-reports can be inaccurate.

In contrast, the UCSF study was based mainly on reports of actual mammograms from seven tumor registries linked with the surveillance program. Of the one million women involved in the study, about 17,000 had breast cancer.

Researchers looked at four separate outcome indicators:

  • stage of disease, the most important predictor of mortality

  • tumor size

  • lymph node involvement

  • tumor grade

Overall, African American women fared worse than whites in all four categories. With stage, tumor size, and lymph node involvement, however, differences between racial and ethnic groups disappeared when patients were grouped in terms of experience with mammography.

But African American women continued to have a higher tumor grade on mammography even when frequency of mammography was accounted for. Reasons were unclear, but the difference could be due to biological, environmental, or social factors. Increased use of mammography may not affect tumor grade outcomes.

It was beyond the scope of the study to look at why women were not undergoing mammography at the same frequency. Smith-Bindman suggests access could be an issue. Women in low-income groups who don't qualify for Medicare or Medicaid may find screening unaffordable.

"This study suggests the need to increase mammography access in communities. There will be opportunities for radiologists to get involved with providers of care to expand access to underserved women," she said.

For more information from the Diagnostic Imaging archives:

NCI study affirms that breast screening saves live

Growth of boutique practice spurs imaging expansion

Mammography systems help keep breast centers on track

After a long haul, digital finally finds an edge

Breast informatics drives health system's quality efforts