Geographic assessment of breast cancer screening by towns, zip codes, and census tracts.

Early detection is the primary way to control breast cancer, and mammography screening can reduce breast cancer mortality 30 to 40 percent among women aged 50 years and older. Geographic areas with a high proportion of cases with late-stage diagnoses may reflect gaps in screening efforts. We used a spatial scan statistic, adjusting for the multitude of possible region locations and sizes, to test whether any particular region of Massachusetts had statistically significant excesses of late-stage diagnoses during the period 1982 to 1986. The novel geographic analysis technique utilized here can also be used in the control of other types of cancer.