Mammography screening and the increase in breast cancer incidence in Hawaii

This ecological study investigated the association between mammography utilization and breast cancer incidence in Hawaii with the hypothesis that geographic areas with high mammography use have higher breast cancer incidence than geographic areas with low mammography use. Insurance claims for mammograms received during 1992 and 1993 were combined with breast cancer incidence data from the Hawaii Tumor Registry and data from the 1990 Census ZIP File. The claims data were obtained from four private and three public health plans and covered approximately 85% of women 40 years of age and older. Age-specific breast cancer incidence rates for the 79 ZIP code areas were regressed on mammography rates and selected aggregate demographic variables using multiple linear regression. An estimated 42% of women 40 years of age and older had received at least 1 mammogram during 1992 and 1993, with the highest rate (45%) in women ages 50-64 years old. Overall, 23% of the variation in age-specific breast cancer incidence could be predicted by mammography utilization, 23% by increasing age, and 4% by higher education. The relationship between mammography use and breast cancer incidence was strongest for women 50-64 years old and for localized disease. The magnitude of the association between breast cancer incidence and mammography utilization was comparable to the increase in breast cancer rates observed in Hawaii during the mid-1980s, supporting the hypothesis that the sharp increase in breast cancer incidence was attributable to screening and early detection. However, the long-term 1% increase in breast cancer incidence requires alternate explanations.