Over the next 25 years, high levels of coverage from the UK’s HPV vaccination and Cervical Screening Programmes should result in greatly reduced incidence and mortality from cervical cancer. The Jo’s Cervical Cancer Trust model considers the long-term combined effect of both prevention programmes; predicting incidence, staging and mortality from cervical cancer up to 2040 in the UK by age under different scenarios relating to the future of these programmes.
The model is flexible and allows for screening and vaccination rates to be adjusted up or down, predicting the impact on incidence and mortality. It also takes into consideration likely changes to both programmes including the use of a 9-valent vaccine and the introduction of HPV primary screening.
The Jo’s Cervical Cancer Trust model uses data from the audit of cervical cancers in England to estimate (by age) the relative risks of cervical cancer by screening attendance. To allow the underlying cancer incidence to change over the next 25 years in the absence of changes to vaccination/screening, a novel age-period-cohort model was fitted to cervical cancer incidence from 1971 to 2013, and extrapolated over the next 25 years. The model estimates mortality by applying stage- and age-specific excess hazards (from published survival data).
For the baseline scenario we assume that screening is by cytology until 2017, when HPV primary testing is fully implemented. We will discuss three scenarios for future screening coverage (100% coverage, current coverage continues, and no future screening) and three vaccine scenarios (current uptake using the quadrivalent vaccine, and change to 9-valent vaccine in 2018). We assume that both vaccines initially prevent all target HPV types (and for the quadrivalent 15% of other high risk HPV types), but that the efficacy wanes by 0.25% per year.
If screening coverage were to be maintained up to 2040 we would see cervical cancer rates decrease by 60% in women under age 45. For older women, particularly those age 60 and over we would see between 10-20% increases in the rates due to strong cohort effects. In a scenario where screening is slowly phased out we would see a doubling of cervical cancer rates by 2040.
The flexibility of the Jo’s Cervical Cancer Trust model allows policy makers to consider the implications of changes to prevention programmes on cervical cancer over the medium- and long-term. Of particular note, with the high vaccination coverage achieved in the UK, the future burden of cancer will shift to older women who have a higher underlying risk of cervical cancer than previous generations.