Cervical cancer screening in Australia: modelled evaluation of the impact of changing the recommended interval from two to three years

The National Cervical Screening Program in Australia currently recommends that sexually active women between the ages of 18-70 years attend routine screening every 2 years. The publically funded National HPV Vaccination Program commenced in 2007, with catch-up in females aged 12-26 years conducted until 2009; and this may prompt consideration of whether the screening interval and other aspects of the organized screening program could be reviewed. The aim of the current evaluation was to assess the epidemiologic outcomes and cost implications of changing the recommended screening interval in Australia to 3 years.

We used a modelling approach to evaluate the effects of moving to a 3-yearly recommended screening interval. We used data from the Victorian Cervical Cytology Registry over the period 1997-2007 to model compliance with routine screening under current practice, and registry data from other countries with 3-yearly recommendations to inform assumptions about future screening behaviour under two alternative systems for screening organisation - retention of a reminder-based system (as in New Zealand), or a move to a call-and-recall system (as in England).

A 3-yearly recommendation is predicted to be of similar effectiveness to the current 2-yearly recommendation, resulting in no substantial change to the total number of incident cervical cancer cases or cancer deaths, or to the estimated 0.68% average cumulative lifetime risk of cervical cancer in unvaccinated Australian women. However, a 3-yearly screening policy would be associated with decreases in the annual number of colposcopy and biopsy procedures performed (by 4-10%) and decreases in the number of treatments for pre-invasive lesions (by 2-4%). The magnitude of the decrease in the number of diagnostic procedures and treatments would depend on the method of screening organization, with call-and-recall screening associated with the highest reductions. The cost savings are predicted to be of the order of A$10-18 M annually, equivalent to 6-11% of the total cost of the current program (excluding overheads), with call-and-recall being associated with the greatest savings.

Lengthening the recommended screening interval to 3 years in Australia is not predicted to result in increases in rates of cervical cancer and is predicted to decrease the number of women undergoing diagnostic and treatment procedures. These findings are consistent with a large body of international evidence showing that screening more frequently than every three years with cervical cytology does not result in substantial gains in screening effectiveness.