Impact of the Australian National Cervical Screening Program in women of different ages.

OBJECTIVES: The Australian National Cervical Screening Program (NCSP) will transition in 2017 from cytology-based screening every two years, starting from age 18-20 years, to HPV-based screening every 5 years, starting from age 25. To examine the impact of the program before this transition we analysed trends in the incidence of cervical cancer, by age and histological subtype.

DESIGN, SETTING AND PARTICIPANTS: National cervical cancer incidence data, 1982-2010.

MAIN OUTCOME MEASURES: Standardised rate ratios (SRR) for 3-yearly average cervical cancer incidence, relative to the rate during 1988-1990, by age group and histological type.

RESULTS: Between 1988-1990 and 2008-2010, cervical cancer incidence fell substantially in women aged 25-49 (SRR, 0.55; 95% CI, 0.51-0.59), 50-69 (SRR, 0.46; 95% CI, 0.42-0.51) and 70 years or more (SRR, 0.50; 95% CI, 0.43-0.58), but not in women aged 20-24 years (SRR, 0.70; 95% CI, 0.46-1.05). These declines were primarily driven by drops in squamous cell carcinoma (SCC) in women aged 25-49 (SRR, 0.50; 95% CI, 0.46-0.55), 50-69 (SRR, 0.39; 95% CI, 0.35-0.45) and more than 70 years (SRR, 0.43; 95% CI, 0.36-0.51). However, rates have now plateaued in women aged 25-69 years. The incidence of adenocarcinoma did not consistently decline across the program period in any age group. The incidence of neither SCC (SRR, 0.91; 95% CI, 0.55-1.51) nor adenocarcinoma (SRR, 0.91; 95% CI, 0.35-2.40) declined in women aged 20-24 years.

CONCLUSION: Although women aged 20-24 years have been included in the NCSP since its inception, no significant impact on cervical cancer incidence was observed in this age group. The NCSP has had a substantial impact on SCC and overall cervical cancer incidence in women aged 25 years and over. Its impact on the incidence of adenocarcinoma, in contrast, has been limited.