Recent increase in incidence of cervical precancerous lesions in Norway: Nationwide study from 1992 to 2016

We analysed patterns in the incidence of cervical intraepithelial neoplasia grades 2 and 3 (CIN2, CIN3) and adenocarcinoma in situ (AIS) by age and histology in 1992-2016 in Norway and described changes in screening tests. Incident cases of CIN2, CIN3, AIS and cervical cancer were identified in the Cancer Registry of Norway, as were all women with at least one screening test. The annual percentage change statistic was used to assess point estimates and changes in age-specific and age-standardised incidence rates (IR). Women aged 25-29 years had the highest incidence of cervical precancerous lesions (CIN2: 192.9/10, CIN3: 737.2/10, AIS: 32.5/10(5) in 2016). The IR of CIN2 increased for all screening ages (25-69 years) from 3.6% to 6.7% per year. CIN3 incidence increased by 1.6% (95% confidence interval [CI] 0.6-2.6) annually. A steep increase in AIS incidence was observed in all age groups (7.1% per year, 95% CI 5.3-8.8). Changes in screening tests and the histological verification of cervical precancerous lesions alone cannot explain the steady increase in incidence we observed over the 25-year study period, and increased exposure to human papillomavirus (HPV) likely plays a role. Age-appropriate treatment of screening-detected cervical precancerous lesions is needed for effective cervical cancer control while avoiding overtreatment and related health risks. In order to perform an appropriate harm-benefit evaluation of cervical cancer control efforts, detailed information on screening technology and background risks, including HPV vaccination status, is needed to create optimal public health policy.