Case-control study of cervical cancer and gynecologic screening: A SEER-Medicare analysis

Objective To determine the association between Pap smear and pelvic examination screenings and the development of invasive cervical cancer in a Medicare population using a matched case-control design. Methods Matched case-control data sets were constructed from the SEER-Medicare database that links the Surveillance Epidemiology End Results (SEER) cancer registry data and Medicare enrollment and claims data of subjects who received care between the years 1991 and 1999 aged 65 years or older. The study identified 1267 cervical cancer cases. Controls (N = 10.137) were matched to cases representing up to eight matched controls (on age and registry geographic location) for a single case. The association between gynecologic screenings and the development of invasive cervical cancer was ascertained using conditional logistic regression analysis. Results Having had a Pap smear during the PIDP (pre-invasive detectable phase – 2 to 7 years prior to diagnosis) was significantly negatively associated with the development of invasive cervical cancer (OR = 0.64, 95% CI = 0.53–0.78) which was reduced after taking into account the estimated prevalence of hysterectomy among controls (OR = 0.38, 95% CI = 0.32–0.46). The negative association between Pap smear screenings and cervical cancer was strongest for squamous tumors (OR = 0.48, 95% CI = 0.37–0.61). Restricting the subjects to those 72 and over did not affect risk. Conclusions There is a reduction in risk for invasive cervical cancer when women over age 65 are screened. This suggests that cervical cancer screening in the aged population may be beneficial.