The Impact and Cost-Effectiveness of Cervical Screening Strategies in Portugal

Despite having a similar healthcare system, Portugal has almost 50% higher cervical cancer incidence than the United Kingdom and twice that of its neighbouring country Spain. This disparity is particularly noteworthy in the European context, where countries who have invested in organised screening have seen significant reductions of the burden of cervical cancer and have started the transition to a molecular-based assessment of risk for progression to cancer enabled by technologies like HPV testing. The overall aim of this thesis was to evaluate the clinical impact and cost-effectiveness of alternative cervical screening strategies in Portugal. This was achieved by (i) identifying the key factors determining burden of cervical cancer in Portugal, (ii) reviewing the literature on model-based evaluations of cervical screening, (iii) parameterising, adapting, and calibrating an existing mathematical model of HPV infection and progression to cervical cancer to Portuguese sexual behaviour, HPV prevalence and cervical cancer incidence, and (iv) evaluating the clinical impact and cost-effectiveness of alternative screening protocols. The first analysis found that cervical cancer incidence and mortality in Portugal would likely have declined more sharply had screening been organised, based on a comparison on burden and risk factors for cervical cancer in England. The review of the literature on modelling cervical screening showed that model calibration to country-specific data is not standard practice yet and that there was only one cost-effectiveness analysis concerning Portugal, which did not investigate the utility of the currently relevant technologies. In the analysis of the impact of alternative screening protocols, our mathematical model predicts that primary HPV DNA screening as part of an organised programme is likely more effective than cytology-based strategies preventing cervical cancer cases. The economic evaluation showed that HPV primary screening with extended interval may be cost-effective but this is highly dependent on the unit cost of HPV DNA testing relative to cytology.