Impact of screening on cervical cancer incidence. A population-based case-control study in the United States

Cervical cancer is widely preventable through screening, but little is known about the duration of protection offered by a negative screen in North America. A case-control study was conducted with records from population-based registries in New Mexico. Cases were obtained from the Tumor Registry diagnosed with cervical cancer in 2006-2016. Five controls per case from the New Mexico HPV Pap Registry were matched to cases by sex, age and place of residence. Dates and results of all cervical screening and diagnostic tests since 2006 were identified from the pap registry. We estimated the odds ratio of non-localized (stage 2+) and localized (stage 1) cervical cancer associated with attending screening in the 3yrs prior to casediagnosis compared to women not screened in 5yrs. Of 876 cases, 527 were aged 25-64y with ≥3yrs of potential screening data. 38% of cases and 61% of controls attended screening in a 3yr period. Women screened in the 3yrs prior to diagnosis had 83% lower risk of non-localized cancer (odds ratio (OR)=0.17,95%CI:0.12-0.24), and 48% lower odds of localized cancer (OR=0.52,95%CI:0.38-0.72), compared with women not screened in the 5yrs prior to diagnosis. Women remained at low risk of non-localized cancer for 3.5-5yrs after a negative screen compared to women with no negative screens in the 5yrs prior to diagnosis. Routine cervical screening is effective at preventing localized and non-localized cervical cancers; 3-yearly screening prevents 83% of non-localized cancers, with no additional benefit of more frequent screening. Increasing screening coverage remains essential to further reduce cervical cancer incidence.