Preventable fractions of cervical cancer via effective screening in six Baltic, central, and eastern European countries 2017-40: a population-based study

Abstract

Background: Cervical cancer incidence remains high in several Baltic, central, and eastern European (BCEE) countries, mainly as a result of a historical absence of effective screening programmes. As a catalyst for action, we aimed to estimate the number of women who could be spared from cervical cancer across six countries in the region during the next 25 years, if effective screening interventions were introduced.

Methods: In this population-based study, we applied age-period-cohort models with spline functions within a Bayesian framework to incidence data from six BCEE countries (Estonia, Latvia, Lithuania, Belarus, Bulgaria, and Russia) to develop projections of the future number of new cases of cervical cancer from 2017 to 2040 based on two future scenarios: continued absence of screening (scenario A) versus the introduction of effective screening from 2017 onwards (scenario B). The timespan of available data varied from 16 years in Bulgaria to 40 years in Estonia. Projected rates up to 2040 were obtained in scenario A by extrapolating cohort-specific trends, a marker of changing risk of human papillomavirus (HPV) infection, assuming a continued absence of effective screening in future years. Scenario B added the effect of gradual introduction of screening in each country, under the assumption period effects would be equivalent to the decreasing trend by calendar year seen in Denmark (our comparator country) since the progressive regional introduction of screening from the late 1960s.

Findings: According to scenario A, projected incidence rates will continue to increase substantially in many BCEE countries. Very high age-standardised rates of cervical cancer are predicted in Lithuania, Latvia, Belarus, and Estonia (up to 88 cases per 100 000). According to scenario B, the beneficial effects of effective screening will increase progressively over time, leading to a 50-60% reduction of the projected incidence rates by around 2040, resulting in the prevention of cervical cancer in 1500 women in Estonia and more than 150 000 women in Russia. The immediate launch of effective screening programmes could prevent almost 180 000 new cervical cancer diagnoses in a 25-year period in the six BCEE countries studied.

Interpretation: Based on our findings, there is a clear need to begin cervical screening in these six countries as soon as possible to reduce the high and increasing incidence of cervical cancer over the next decades.

Funding: None.

Figure 1

Observed and projected incidence of cervical cancer in six Baltic, central, and eastern European countries Forecasts of future cervical cancer rates according to two scenarios: no screening (red circles) and effective screening commencing in 2017 (purple circles). The introduction of effective screening shows a progressive effect similar to that recorded in Denmark after the introduction of screening in the 1960s.

Figure 2

Estimated percentage of cervical cancer cases expected to be potentially preventable by screening in 2040 in six Baltic and eastern European countries The percentage of cervical cancer cases prevented is calculated as: projected 1–projected 2 × 100/projected 1. Projected cases are derived from a modified age–period–cohort model. Projected 1=projected cases in a scenario that assumes no improvements in present cervical cancer screening activities (scenario A). Projected 2=projected cases in a scenario that assumes that effective screening will start in 2017 (scenario B).