Introducing human papillomavirus (HPV) primary testing in the age of HPV vaccination: projected impact on colposcopy services in Wales

Colposcopy referral rates post-introduction of primary screening with human papillomavirus testing: evidence from a large British Columbia cohort study

Background

Shifting from cytology to human papillomavirus (HPV)-based cervical cancer screening will initially increase colposcopy referrals. The anticipated impact on health systems has been raised as a concern for implementation. It is unclear if the higher rate of colposcopy referrals is sustained after initial HPV-based screens or reverts to new lower baselines due to earlier detection and treatment of precancer. This study aimed to investigate long-term rates of colposcopy referrals after participation in HPV-based screening.

Methods

Participants of HPV for Cervical Cancer Screening trial (HPV FOCAL) received one (HPV1, N = 6204) or two (HPV2, N = 9540) HPV-based screens. After exit, they returned to British Columbia's (BC) cytology screening program. A comparison cohort from the BC screening population (BCS, N = 1,140,745) was identified, mirroring trial inclusion criteria. All participants were followed for 10-14 years through the provincial screening registry. Colposcopy referral rates per 1000 screens were calculated for each group. Trial colposcopy referrals for HPV1 and HPV2 were calculated under two referral scenarios: (1) all HPV positive referred to colposcopy; (2) cytology triage with ASCUS or greater referred to colposcopy. Colposcopy referrals from post-trial screens in HPV1 an HPV2 and all screens in BCS were based on actual recommendations from the screening program. A multivariable flexible survival regression model compared hazard ratios (HR) throughout follow-up.

Findings

Scenario 2 referral rates were higher during initial HPV screen(s) vs cytology screen (HPV1: 28 per 1000 screens (95% CI: 24, 33), HPV2: 32 per 1000 screens (95% CI: 29, 36), BCS: 8 per 1000 screens (95% CI: 8.9)). However, post-trial rates in HPV1 and HPV2 were significantly lower than in BCS. Cumulative rates in HPV1 and HPV2 approached the cumulative rate in BCS 11-12 years after HPV-based screening (HPV1: 11 per 1000 screens (95% CI: 10, 12), HPV2: 16 per 1000 screens (95% CI: 15-17), BCS: 11 per 1000 screens (95% CI: 10, 11)). Adjusted models demonstrated reductions in referral rates in HPV1 (HR = 0.6, 95% CI: 0.5, 0.7) and HPV2 (HR = 0.7, 95% CI: 0.6, 0.8) relative to BCS by 54 and 72 months post-final HPV screen respectively.

Interpretation

Reduced colposcopy referral rates were observed after initial rounds of HPV-based screening. After initial HPV screening, referral rates to colposcopy after cytology triage were below the current rates seen in a centralized cytology program after approximately four years. Any expected increase in referrals at initiation of HPV-based screening could be countered by staged program implementation.

Funding

This work was supported by the National Institutes of Health (R01 CA221918), Michael Smith Health Research BC (RT-2021-1595), and the Canadian Institutes of Health Research (MCT82072).

Managing an extension of screening intervals: Avoiding boom and bust in health care workloads

Extending screening intervals in ongoing cancer screening programmes can lead to challenging year-on-year variations in the number of screening tests. We explored how such variation could be diminished with a managed transition to the extended interval. We defined three extension scenarios: immediate extension for the entire target population; stepped transition by birth cohort; and gradual transition by reducing the number of available screening appointments. These were compared to a situation in which the interval remains unchanged in a demographic model covering a 15-year period. The model was populated with observed parameters from England, a real-world setting recommending cervical screening with 3-year intervals at age 25-49 and 5-year intervals at age 50-64. Informed by typical changes currently considered by several European programmes including the programme in England, we explored the effect on screening test numbers of an extension of the 3-year interval to 5 years for women younger than 50. All three extension scenarios resulted in similar cumulative numbers of screening tests, which were about 30% lower compared to a situation in which the interval would remain unchanged. However, the year-on-year variation in the number of screening tests varied between the scenarios. This variation was around 4-fold for the immediate scenario. In the stepped scenario, the yearly numbers could differ by around 20%, whereas in the gradual scenario they were virtually constant. A managed interval extension, transitioning different groups of the target population at different times, can substantially reduce the yearly variation in screening workload without increasing the total number of screening tests in the long term.

Which is the best management for women with normal cervical cytologic findings despite positivity for non-16/18 high risk human papillomaviruses?

Women who test positive for the human papillomavirus (HPV) but have normal cytology constitute the predominant subgroup of patients in the screening population in the post-vaccination era. The distribution of HPV genotypes changed dramatically, which was attributable to an increase in HPV vaccination coverage. These changes have created uncertainty about how to properly manage women with normal cytology, non-HPV16/18 infections, or persistent infections. Current recommendations include retesting and continued surveillance in the absence of HPV16/18 infection. However, these are not always applicable. The ability to implement genotyping or incorporate HPV16/18 with some additional high-risk HPV (HR-HPV) types for triage and management with the aim of identifying type-specific risks in this population could be acceptable. When the next set of guidelines is updated, generating potential triage strategies for detecting high-grade cervical lesions, such as the p16/Ki67 cytology assay and other alternatives that incorporate genotyping with newer tests, should be considered. Current clinical management is shifting to risk-based strategies; however, no specific risk threshold has been established in this population. Importantly, innovative triage testing should be evaluated in combination with primary screening and management. Furthermore, there is an untapped opportunity to coordinate HPV genotyping in combination with colposcopic characteristics to modify risk in this group. Hence, providing a more personalized schedule through the efficient application of risk stratification and improving the detection of pre-cancer and cancer is an option worth exploring.

Shift in harms and benefits of cervical cancer screening in the era of HPV screening and vaccination: a modelling study

Objective

To calculate the changes in harms and benefits of cervical cancer screening over the first three screening rounds of the Dutch high‐risk human papillomavirus (hrHPV) screening programme.

Design

Microsimulation study.

Setting

Dutch hrHPV screening programme; women are invited for screening every 5 or 10 years (depending on age and screening history) from age 30 to 65.

Population

Partly vaccinated population of 100 million Dutch women.

Methods

Microsimulation model MISCAN was used to estimate screening effects. Sensitivity analyses were performed on test characteristics and attendance.

Main outcome measures

Harms (screening tests, unnecessary referrals, treatment‐related health problems), benefits (CIN2⁺ diagnoses) and programme efficiency (number needed to screen [NNS]) over the first (period 2017–2021), second (period 2022–2026) and third (period 2027–2031) rounds of hrHPV‐based screening.

Results

The number of screening tests and CIN2⁺ diagnoses decreased from the first to the second round (−25.8% and −23.6%, respectively). In the third screening round, these numbers decreased further, albeit only slightly (−2.7% and −5.3%, respectively). NNS to detect a CIN2⁺ remained constant over the rounds; however, it increased in younger age groups while decreasing in older age groups.

Conclusion

Both harms and benefits of hrHPV screening decreased over the first screening rounds. For younger women, the efficiency would decrease, whereas longer screening intervals would lead to increased efficiency in older women. Programme efficiency overall remained stable, showing the importance of longer intervals for low‐risk women.

Tweetable abstract:

Cervical cancer screening: both harms and benefits of hrHPV screening will decrease in the future.

Cervical cancer screening: both harms and benefits of hrHPV screening will decrease in the future.

Introducing human papillomavirus (HPV) primary testing in the age of HPV vaccination: projected impact on colposcopy services in Wales

OBJECTIVE

To determine the demand for colposcopy in the Cervical Screening Wales programme after the introduction of human papillomavirus (HPV) cervical screening, which coincided with the start of screening of women vaccinated against HPV types 16/18.

DESIGN

The study used a computational model that assigns screening and screening-related colposcopy events to birth cohorts in individual calendar years.

SETTING

Cervical Screening Wales.

POPULATION

Women aged 25-64 years from birth cohorts 1953-2007.

METHODS AND MAIN OUTCOME MEASURES

We estimated the numbers of colposcopies and high-grade cervical intraepithelial lesions (CIN2+) within Cervical Screening Wales in 2018-32, using official population projections for Wales and published estimates of the effects of HPV screening and vaccination.

RESULTS

Vaccination will reduce the number of colposcopies by 10% within the first 3-4 years after the national roll-out of HPV screening, and by about 20% thereafter. The number of screening colposcopies is estimated to increase from 6100 in 2018 and peak at 8000 (+31%) in 2021, assuming current screening intervals are maintained. The numbers of CIN2+ lesions follow similar patterns, stabilising at around 1000 diagnoses per year by 2026, approximately 60% lower than at present. Extending the screening intervals to 5 years for all women shows similar trends but introduces peaks and troughs over the years.

CONCLUSIONS

Vaccination will not fully prevent an increase in colposcopies and detected CIN2+ lesions during the first 2-3 years of HPV-based screening but the numbers are expected to decrease substantially after 5-6 years.

TWEETABLE ABSTRACT

HPV-based cervical screening will initially increase colposcopy referral. In 6 years, this increase will be reversed, partly by HPV vaccination.