The impact of mammography utilization on breast cancer incidence in Hawaii

Abstract

This research is an ecologic study investigating the association between mammography utilization and breast cancer incidence in Hawaii with the hypothesis that geographic areas with high mammography rates have higher breast cancer incidence rates than geographic areas with low mammography rates. Insurance claims for mammograms received during 1992/93 were combined with breast cancer incidence data from the state-wide Hawaii Tumor Registry, the 1990 Census ZIP File, and death records. Insurance claims data were obtained from four private and three public health plans and covered approximately 85% of the state's female population age 40 years old and older. Age-specific breast cancer incidence rates for each of the 79 ZIP code areas were regressed on mammography rates and selected demographic variables using both multiple linear and multiple logistic regression. An estimated 42% of women 40 years old and older had received at least one mammogram during the study period 1992 to 1993, with the highest rate (45%) in women 50 to 64 years old. Overall, 23% of the variation in age-specific breast cancer incidence was associated with mammography utilization, another 23% with age, and 4% with educational attainment. The relation between mammography use and breast cancer incidence was strongest for women 50 to 64 years old and weakest for women 40 to 49 years old. Mammography utilization predicted 17% of the variance in localized disease, but very little of the variance of in situ or advanced disease. Neither mammography utilization nor demographic variables were found to be good predictors of geographic variations in breast cancer mortality in Hawaii. In summary, geographic areas in Hawaii with high mammography utilization experienced higher breast cancer incidence rates than areas with low mammography utilization. The size of this effect was consistent with the increase in breast cancer rates observed since the mid-eighties, supporting the hypothesis that the increase in breast cancer incidence is attributable to screening and early detection. However, the long term increase in breast cancer incidence requires alternate explanations.