Is Mammography Useful in Older Women

摘要

Despite the fact that approximately 43% of all breast cancers occur in women over 7O years of age, no previous randomized controlled trial (RCT) addressed women in this age group. Without clear evidence, the usefulness of the mammograms currently performed on 15-36% of women over age 7O is unknown. We present the use of an administrative utilization database linked to breast cancer outcomes to examine the usefulness of mammography in women age 7O and older. Using the Linked medicare-SEER Tumor Registry Database, created by the National Cancer Institute and the Health Care Financing Administration, we have created a database of 9767 women diagnosed with breast cancer from January 1, 1987 to December 31, 1993, and compared mammography users versus nonusers on stage of presentation, all cause survival and breast cancer survival. Women over 70 years who were nonusers of mammography were diagnosed with breast cancer at Stage II or greater more often than regular users (adjusted odds ratio (OR), 3. 12 95% CI, 2.74-3.58). Nonusers of mammography were at significantly greater risk of dying from their breast cancer than regular users for all women (adjusted hazard ratio (HR), 3.38 95% CI, 2.65-4.32) and for women within each age group. Even assuming a lead- time of 1.25 years, nonusers of mammography continued to be at increased risk of dying from breast cancer. In order to account for selection bias since we are dealing with observational data, we employed two methods. First, we used propensity score matching to reduce the sample to a simulation of a randomized study. Second, we used instrumental variable analysis to look at unmeasured covariates which are unassociated with region of the country that might affect our outcome. In each case, we showed that there was only a minimal change in the adjusted odds ratio of stage at diagnosis (3.27 and 3.01, respectively) .