Efficacy of Cervical Cancer Screening to Prevent Cervical Cancer Mortality Among Women Ages 55 to 79 Years: A Population-Based, Case-Control Study

Thesis (Ph.D.)--University of Washington, 2013Aim. Though cervical cytology screening has been shown to reduce cervical cancer incidence and mortality among reproductive-age women, there are but limited data regarding the efficacy of screening older women. Analyses from Sweden and Finland suggest that participation by older women in organized cytology screening programs reduces the incidence of cervical cancer by 51-64%. In the United States, results from Kamineni and colleagues suggest that cytology screening reduces cervical cancer incidence by 77% among women ages 55-79 years. We sought to quantify the efficacy of cervical cancer screening among older American women with respect to mortality. Methods. Among enrollees of two U.S. health plans, we compared cervical screening histories of women ages 55-79 who died of cervical cancer during 1980-2010 (cases) to those of women who were at risk of developing this malignancy (controls). Controls were sampled from women with an intact cervix, matched 2:1 to cases on health plan, age, and enrollment duration. Medical records were reviewed to ascertain each woman's receipt of cytology screening during the detectable pre-clinical phase (DPP), estimated to be the 5 to 7 years prior to diagnosis during which cervical neoplasia is asymptomatic but cytologically detectable. Logistic regression models were used to estimate the risk of cervical cancer mortality associated with screening. Results. 39 cases and 80 controls were eligible for the study. Screening during the presumed DPP was associated with a 74% (95% CI: 37-90%) reduction in cervical cancer mortality, adjusting for matching characteristics and covariates that were associated with case status (smoking, marital status, race/ethnicity). Significance. Screening of older women by means of cervical cytology was strongly associated with reduced cervical cancer mortality. These results provide a minimum efficacy estimate of human papillomavirus DNA screening - a more sensitive test that may be increasingly utilized in the future -- to reduce mortality among older women