Prior research indicates that women who are treated for cervical intraepithelial neoplasia (CIN) remain at increased risk of developing cervical cancer when compared with women with normal cytology results or women in the general population. However, several are limited by small study populations, use of different CIN grades, or lack of information on post-treatment follow-up.

To estimate the risk of cervical cancer in women with a history of CIN grade 3 (CIN3) and review the compliance with post-treatment follow-up, my colleagues and I conducted a retrospective cohort study in 80,442 women with a CIN3 diagnosis between 1990 and 2010, with cases of recurrent CIN3 and cervical cancer identified until 2016.

After a median follow-up of 15.8 years and 1,278,297 person years, 1,554 women (1.9%) developed recurrent CIN3 and 397 women (0.5%) cervical cancer. Women with CIN3 had a twofold increased risk of cervical cancer when compared with the general female population. This risk was highest between 5 and 9 years of follow-up (Figure). Increased risk of cervical cancer was seen at up to 20 years, but this seems to be mostly attributable to aging. Women with recurrent CIN3 had a ninefold increased risk of developing cervical cancer, while women aged 50 and older at CIN3 diagnosis had a sevenfold increased risk. Women older than 60 had a sixfold greater incidence of cervical cancer, suggesting that women treated for CIN3 are in need of an adjusted long-term follow-up program, as well as that screening only until age 60 is insufficient.

With 37% of women who developed cervical cancer not completing the advised post-treatment follow-up, further research is needed to optimize follow-up strategies and to investigate if women treated for CIN3 may benefit from adjuvant high-risk HPV vaccination.