Identification and measurement of disparities in screening are critical to substantially improve rates of mammography screening in local community settings. Previous studies have reported individual-level risk factors and census-tract socioeconomic effect on mammography use.7,8,22–27,29,30,32–34,43
In our study, system-level barriers to mammography and heavy smoking were associated with mammography use among white and African American women. Personal-experience barriers to mammography and no physician recommendation also were independently associated with mammography screening among white women. White women but not African American women residing in a historic geographic cluster area of late-stage breast cancer were less likely to have mammograms. Increased risk of late-stage breast cancer in women age 40 or older can result from nonadherence to recommended breast cancer screening guidelines or from failure to have timely and adequate follow-up of positive screening results or of an actual breast cancer diagnosis. In community settings, nonadherence to breast cancer screening guidelines contributes to the increased risk of late-stage breast cancer among women more than 40 years of age.2
Thus, it is reasonable to target efforts to improve adherence to mammography screening guidelines in a geographic area previously found to have higher-than-expected incidence of late-stage breast cancer.
The rates of mammography screening use in the City of St. Louis were 69.5% within and 70.6% outside the geographic cluster of elevated incidence of late-stage breast cancer; these rates are slightly lower than the 74.6% nationally reported on the BRFSS.10
Our results show that before and after adjusting for four groups of individual-level variables, significantly higher mammography use was found for African American compared with white women. Although unexpected, this reverse racial difference is similar to a previous study6
and suggests that mammography screening rates may have been successfully improved, to some degree, among African American women living in the City of St. Louis. Recent studies also indicated women residing in areas with higher percentage of non-Hispanic African American women were more likely to have mammograms.7,8
Additionally, our study also indicated that white women residing within the geographic cluster of late-stage breast cancer diagnosis had lower mammography screening relative to the rest of the city. These findings suggest a need to increase routine-screening mammography use among white women, especially for those living within the cluster area. Although we have examined 16 individual-level factors previously reported to be associated with mammography use, these factors did not fully explain why white women living within the St. Louis City limits overall and white women who lived in the cluster area were less likely to receive mammograms. Possible explanations for these findings could include individual-level factors that we did not measure, such as incentives for primary care physicians,44
a woman’s perceived susceptibility to breast cancer,45
or travel distance to mammography facilities.46
Contextual factors, such as spatial availability and accessibility of low-fee or no-fee screening mammography, also could play a role.47
Future studies focusing on these factors will provide support for the effectiveness of targeted interventions, such as flexible clinic hours, health education, or provision of services using mobile mammography vans. Although previous studies have found socioeconomic position to be an important indicator of breast cancer screening, neither individual-level nor census-tract-level socioeconomic status was found to be associated with mammography screening in our study.
In this study, we only surveyed women in the City of St. Louis, which was previously identified in the analysis of Missouri statewide data as having a cluster of increased incidence of late-stage breast cancer. Therefore, our results may not be directly generalized to other geographic areas in Missouri or elsewhere. For example, it has been reported that rural residents were less likely to receive preventive healthcare services than urban residents.7,8,48
Our findings, however, suggest that a historic geographic cluster of late-stage breast cancer may serve as a geographic marker for nonadherence to recommended breast cancer screening, so we can better target interventions to improve mammography screening in areas of greater need. Since the proportion of cases of late-stage (distant) breast cancers changed little over time in the City of St. Louis according to the Missouri Cancer Registry (from 40.2% in 1996–1998 to 43.3% in 2002–2004),49
it is unlikely that the cluster of late-stage breast cancer has disappeared. Although it still remains unclear why late-stage breast cancer aggregated in this area, we can speculate this cluster may result partly from lower rates of mammography use. Although our study did not indicate that African American women also had a lower mammography screening in this area, other research has reported that African American women were less likely to receive adequate follow-up of abnormal mammographic results than white women.50,51
This observation might partially explain the clustering of late-stage breast cancer cases in this area.
Other limitations include our reliance on telephone interviews. Since low-income households are less likely to have telephones or may be more likely to have intermittent telephone service and since they are more likely to be located in the geographic cluster of elevated late-stage breast cancer incidence, this limitation could have biased our findings. However, such bias would have underestimated our findings.