Risk of cervical and other cancers after treatment of cervical intraepithelial neoplasia: retrospective cohort study

Objective To study the long term risk of cervical and other cancers after treatment for cervical intraepithelial neoplasia. Design Retrospective Cohort study. Setting University Hospital, Helsinki, Finland. Participants 7564 women treated for cervical intraepithelial neoplasia during 1974 and 2001 and followed tip through the Finnish cancer registry until 2003. Main outcome measures Standardised incidence ratio for cervical cancer and other cancers. Results During follow-up 22 cases of invasive cervical cancer occurred in women treated for cervical intraepithelial neoplasia (standardised incidence ratio 2.8, 95% confidence interval 1.7 to 4.2). The highest risk was during the second decade (10 cases observed: 3.1, 1.5 to 5.7). The standardised incidence ratio for cervical intraepithelial cancer type 1 was 3.1 (1.4 to 6.2) and for type 2 was 3.7 (0.9 to 10.7). Conclusions The risk of cervical cancer in the first 20 years after treatment for cervical intraepithelial neoplasia is higher than in the average population. The risk of smoking related cancers is also increased.