Clinical course of cervical intraepithelial neoplasia grade 2: a population-based cohort study

Cervical intraepithelial neoplasia grade 2 has historically been the threshold for surgical excision, but because of high regression rates, many countries are transitioning to active surveillance. However, estimates for regression rates are based on small studies with heterogeneous definitions of regression and progression.This study aimed to describe regression and progression rates of cervical intraepithelial neoplasia grade 2 using nationwide healthcare registry data.This was a nationwide population-based cohort study on women aged 18 to 40 years who had undergone active surveillance for cervical intraepithelial neoplasia grade 2 in Denmark from 1998 to 2020. This study excluded women with a previous record of cervical intraepithelial neoplasia grade 2 or worse or surgical excision. Cumulative incidence functions were used to estimate the rates of regression and progression at 6, 12, 18, and 24 months after diagnosis. In addition, a modified Poisson regression was used to estimate the crude and adjusted relative risks of progression within 24 months stratified by index cytology and age.During the study period, 11,056 women underwent active surveillance, 6767 of whom regressed and 3580 of whom progressed within 24 months. This corresponded to regression rates of 62.9% (95% confidence interval, 61.9-63.8) and progression rates of 33.3% (95% confidence interval, 32.4-34.2) at 24 months of follow-up. Most women regressed (90%) or progressed (90%) within the first 12 months. Women with high-grade index cytology had a higher risk of progression than women with normal index cytology (adjusted relative, 1.58; 95% confidence interval, 1.43-1.76), whereas there was no difference in the risk of progression between women aged 30 and 40 years and women aged 23 to 29 years (adjusted relative risk, 0.98; 95% confidence interval, 0.88-1.10).The observed high regression rates of cervical intraepithelial neoplasia grade 2 supported the transition in clinical management from surgical excision to active surveillance, particularly among women with low-grade or normal index cytology.