Alejandra Castanon

Exposure Definition in Case–Control Studies of Cervical Cancer Screening: A Systematic Literature Review

Abstract The first step in evaluating the effectiveness of cervical screening is defining exposure to screening. Our aim was to describe the spectrum of screening exposure definitions used in studies of the effectiveness of cervical screening. This systematic review included case-control studies in a population-based screening setting. Outcome was incidence of cervical cancer. Three electronic databases were searched from January 1, 2012 to December 6, 2018. Articles prior to 2012 were identified from a previous review. The qualitative synthesis focused on describing screening exposure definitions reported in the literature and the methodologic differences that could have an impact on the association between screening and cervical cancer. Forty-one case–control studies were included. Six screening exposure definitions were identified. Cervical cancer risk on average decreased by 66% when screening exposure was defined as ever tested, by 77% by time since last negative test, and by 79% after two or more previous tests. Methodologic differences included composition of the reference group and whether diagnostic and/or symptomatic tests were excluded from the analysis. Consensus guidelines to standardize exposure definitions are needed to ensure evaluations of cervical cancer screening can accurately measure the impact of transitioning from cytology to human papillomavirus–based screening and to allow comparisons between programs.

Technological advances: Have they improved standards? Review of outcomes from the Welsh cervical screening programme

Objectives Introduction of new technologies into cervical screening programmes has allowed more efficient programmes with less resources. We present an overview of screening technologies introduced into the Cervical Screening Wales programme and their evolution over time. Methods Data from the programme’s statistical report were used to evaluate its performance over a 17-year period between 2001/02 and 2017/18. Results The introduction of liquid-based cytology has had a substantial impact on reducing inadequate sample rates and on increasing the positive predictive value of cytology. Inadequate rates have increased following the implementation of human papilloma virus testing as a triage test for cytology. Further knock-on effects on standard reporting ranges are expected following the introduction of human papilloma virus testing as the primary screening test. New performance standards have been introduced to better reflect the performance of the programme at a time when disease prevalence is expected to fall as women vaccinated against human papilloma virus reach screening age. Conclusions Improvements to this cervical cancer screening programme as illustrated through performance indicator ranges suggest a major role played by technology.

Impact of changes to cervical screening guidelines on age and interval at which women are tested: Population-based study

Background English cervical screening programme guidelines changed between 2009 and 2012. We explore the impact on the age and intervals at which women receive a cytology test. Methods Eligible women were controls from a population-based case–control study in England. Tests taken between 1980 and 2017 were extracted from the call/recall database. Using the Kaplan–Meier estimator by birth cohort and age at (or time since) last test, we explore proportions tested since or prior to a given age, years since previous test, and interval following a negative test. Results Screening histories from 46,037 women were included. Proportion tested by age 26 has increased from 55% among birth cohorts 1978–1979 to 67% among those born 1990–1991, despite more recent cohorts only having received one invitation (instead of two) prior to age 26. The proportion of women tested at aged 28 with a test three years earlier increased by 20% (from 36% in 1997–2006 to 56% in 2012–2017) whereas the proportion tested at ages 23–27 without a prior test increased from 34% to 80%. The age at last test prior to exiting the programme has decreased: among those born 1928–1931 86% had a test aged 60–65, but only 71% of those born 1947–1951. Conclusion Clear programme guidance alongside quality assurance has improved the cervical screening programme by standardising the age and intervals at which women are screened.

Acceleration of cervical cancer diagnosis with human papillomavirus testing below age 30: Observational study

AbstractSeveral international cervical screening guidelines advise against using high‐risk human papillomavirus (HR‐HPV) testing in women younger than 30. The rationale for this in young women, lies in the potential for additional detection of both low‐grade and high‐grade cervical intraepithelial neoplasia (CIN) leading to unnecessary treatments without reducing the burden of cervical cancer. We studied 56 544 women screened at 24 to 29 with HR‐HPV testing and 116 858 screened with liquid‐based cytology (LBC) in the English HPV screening pilot. They were compared to 528 460 women screened at the age of 30 to 49. We studied the detection of cervical cancer and CIN2/3 across two consecutive screening rounds 3 years apart. At 24 to 29, a positive HR‐HPV test detected more cases of cervical cancer in the prevalence round than did a positive LBC test (1.36/1000 screened vs 0.82/1000, ORadj: 1.61, 95% CI: 1.18‐2.19). In women with a negative HR‐HPV test, cervical cancer was diagnosed before or at the incidence round in 0.07/1000. After a negative LBC test, cancer detection reached 0.47/1000 and 40% of these cases were diagnosed at FIGO stage IB+. HR‐HPV testing increased the detection of CIN2/3 diagnoses in two consecutive rounds combined by 30% (71.9/1000 vs 55.2/1000). The patterns of detection of cervical cancer and CIN2/3 were almost identical at older ages. These data support using HR‐HPV testing for screening of women younger than 30, which not only accelerates the diagnosis of cervical cancer but leads to a similar relative increase in CIN2/3 diagnosis to that found in women aged 30 to 49.

Recovery strategies following COVID-19 disruption to cervical cancer screening and their impact on excess diagnoses

Abstract Background The COVID-19 pandemic has disrupted cervical cancer screening services. Assuming increases to screening capacity are unrealistic, we propose two recovery strategies: one extends the screening interval by 6 months for all and the other extends the interval by 36/60 months, but only for women who have already missed being screened. Methods Using routine statistics from England we estimate the number of women affected by delays to screening. We used published research to estimate the proportion of screening age women with high-grade cervical intraepithelial neoplasia and progression rates to cancer. Under two recovery scenarios, we estimate the impact of COVID-19 on cervical cancer over one screening cycle (3 years at ages 25–49 and 5 years at ages 50–64 years). The duration of disruption in both scenarios is 6 months. In the first scenario, 10.7 million women have their screening interval extended by 6 months. In the second, 1.5 million women (those due to be screened during the disruption) miss one screening cycle, but most women have no delay. Results Both scenarios result in similar numbers of excess cervical cancers: 630 vs. 632 (both 4.3 per 100,000 women in the population). However, the scenario in which some women miss one screening cycle creates inequalities—they would have much higher rates of excess cancer: 41.5 per 100,000 delayed for screened women compared to those with a 6-month delay (5.9 per 100,000). Conclusion To ensure equity for those affected by COVID-19 related screening delays additional screening capacity will need to be paired with prioritising the screening of overdue women.

COVID-19 disruption to cervical cancer screening in England

Introduction In England, routine invitations for cervical screening were reduced between April 2020 and June 2020 due to the COVID-19 pandemic. We quantify the impact of COVID-19 disruptions on attendance and excess diagnoses of cervical cancer (CC). Methods Using Public Health England CC screening data on laboratory samples received in 2018 as a baseline we quantify the reduction in screening attendances due to the COVID-19 pandemic between April 2020 and March 2021 for women aged 25–64. We model the impact on excess CC diagnoses assuming once invitations resume 87.5% of women attend within 12 months and 12.5% delay screening for 3 or 5 years (depending on age). Results The number of samples received at laboratories was 91% lower than expected during April, 85% during May and 43% during June 2020 compared to the same period in 2018. Although on average laboratories received 12.6% more samples between August 2020 and April 2021 than over the same months in 2018, by April 2021 there was a short fall of 200,949 samples (6.4% fewer than in 2018). An excess of 41 CC (4.0 per 100,000 women with a maximum screening delay of 12 months) are predicted to occur among the estimated 1,024,794 women attending this screening round with a delay. An excess of 60 CC (41.0 per 100,000 women) are predicted to occur among the estimated 146,391 women who do not attend this screening round. Conclusion Prompt restoration of cervical screening services limited the impact on excess CC diagnoses. However, in 2020 a 6.4% shortfall of screening samples was observed. Every effort should be made to reassure these women that services are open and safe to attend.