Reason for Late-Stage Breast Cancer: Absence of Screening or Detection, or Breakdown in Follow-up?

Abstract

Mammography screening increases the detection of early-stage breast cancers. Therefore, implementing screening should reduce the percentage of women who are diagnosed with late-stage disease. However, despite high national mammography screening rates, late-stage breast cancers still occur, possibly because of failures in screening implementation. Using data from seven health care plans that included 1.5 million women aged 50 years or older, we conducted retrospective reviews of chart and automated data for 3 years before 1995-1999 diagnoses of late-stage (metastatic and/or tumor size > or =3 cm; case subjects, n = 1347) and early-stage breast cancers (control subjects, n = 1347). We categorized the earliest screening mammogram during the period 13-36 months before diagnosis as none (absence of screening), negative (absence of detection), or positive (potential breakdown in follow-up). We compared the proportion of case and control subjects in each category of screening implementation and estimated the likelihood (odds ratio [OR] with 95% confidence intervals [CIs]) of late-stage breast cancer. We also evaluated demographic characteristics associated with absence of screening in women with late-stage disease. All statistical tests were two-sided. Absence of screening, absence of detection, and potential breakdown in follow-up were distributed differently among case (52.1%, 39.5%, and 8.4%, respectively) and control subjects (34.4%, 56.9%, and 8.8%, respectively) (P = .03). Among all women, the odds of having late-stage cancer were higher among women with an absence of screening (OR = 2.17, 95% CI = 1.84 to 2.56; P<.001). Among case patients, women were more likely to be in the absence-of-screening group if they were aged 75 years or older (OR = 2.77, 95% CI = 2.10 to 3.65), unmarried (OR = 1.78, 95% CI = 1.41 to 2.24), or without a family history of breast cancer (OR = 1.84, 95% CI = 1.45 to 2.34). A higher proportion of women from census blocks with less education (58.5% versus 49.4%; P = .003) or lower median annual income (54.4% versus 42.9%; P = .004) were in the absence-of-screening category compared with the proportion for the other two categories combined. To reduce late-stage breast cancer occurrence, reaching unscreened women, including elderly, unmarried, low-income, and less educated women, should be made a top priority for screening implementation.