Geographic Clustering of Adequate Diagnostic Follow-Up after Abnormal Screening Results for Breast Cancer among Low-income Women in Missouri

Purpose: In an effort to examine a cluster of late-stage breast cancer, this study reports (1) the extent of geographic variation in adequacy of diagnostic follow-up (ADFU) after abnormal breast cancer screening results across Missouri's counties and census tracts, (2) whether various personal characteristics or area poverty account for any geographic clustering observed, and (3) the association between area poverty rate and ADFU. Methods: We used 1998-2002 Missouri Show Me Healthy Women breast and cervical cancer program data from 2580 low-income women aged 50-64 who had abnormal breast cancer screening results. ADFU was based on established guidelines. Poverty rate was from the 2000 census data. We used 3 complementary statistical approaches. Results: Overall, 26.9% of screening results were inadequately followed up. County-level geographic variation accounted for 6.7% of the total variance in ADFU, while the census-tract-level variation was negligible. Women's sociodemographic characteristics, symptoms reported at time of screening, and screening results accounted for 25% of the county-level variation in ADFU. Statistically significant geographic variation in ADFU remained that could not be explained. Beyond 70 miles from the women's residence, the likelihood of receiving ADFU was geographically uncorrelated. We identified one large geographic cluster extending beyond the borders of counties and census tracts where women were less likely to receive ADFU (relative risk = 0.64; p = 0.01). Conclusions: Efforts to improve the likelihood of ADFU should be directed at examining the relative contributions of the healthcare and social environments and characteristics of the women in the area where women were less likely to receive ADFU especially in the cluster area of late-stage breast cancer rather than targeting efforts at the county or census-tract level.