Purpose: The incidence of cervical cancer, including squamous cell carcinoma (SCC), has been decreasing in several developed countries since the onset of organized screening programs; in some countries, however, the incidence of adenocarcinoma has increased among young women. We investigated the Danish incidence trends during 1997-2011 when cervical screening coverage was high. Incidences of cervical intraepithelial neoplasia grade 3 (CIN3) and adenocarcinoma in situ (AIS) were also assessed, with the latest part of the study period coinciding with introduction of free-of-charge human papillomavirus (HPV) vaccination.
Methods: Using nationwide registries, we estimated age-specific and age-standardized incidence rates and estimated annual percentage change (EAPC).
Results: The incidence of SCC decreased significantly, especially in women aged ≥45 years [EAPC: -3.1 % (95 % CI -4.3 to -2.5)], whereas the incidence of adenocarcinoma increased significantly, from 2.4 to 3.1/100,000 primarily due to increases in women aged ≤44 years [EAPC: 4.3 % (95 % CI 1.8-6.7)]. The incidences of CIN3 and AIS increased significantly from 94.7 to 156.5/100,000 and 3.3 to 11.3/100,000, respectively, but, importantly, they decreased significantly during 2009-2012 in women aged ≤20 years.
Conclusions: The Danish screening program has successfully reduced the incidence of cervical cancer, especially of SCC in older women; however, the program has not significantly reduced the incidence in young women or the incidence of adenocarcinoma, which is increasing. Decreases in the incidences of CIN3 and AIS in age groups with high HPV vaccine coverage may herald a future decrease in cervical cancer incidence in young Danish women.