Objective: To determine factors influencing long term risks for acquiring or dying from invasive cervical or vaginal cancer in women previously treated for cervical intraepithelial neoplasia grade 3 (CIN3).
Design: Population based cohort study conducted in 1958-2008, followed up until 2009 in the Swedish Cancer Registry and Swedish Cause of Death Register, linked to the Swedish Population Register. Standardised incidence and mortality ratios were calculated for the risk of acquiring or dying from vaginal or cervical cancer, with the general female population in Sweden as reference. Relative risks in multivariable regression models were also calculated, adjusting for follow-up duration, treatment period, and age at CIN3 treatment or attained age.
Setting: Entire female population of Sweden.
Participants: 150,883 women in Sweden diagnosed and treated with CIN3 and followed up for invasive cervical or vaginal cancer, and related mortality. The cohort comprised 3,148,222 woman years.
Main outcome measures: Standardised incidence and mortality ratios, stratified by period for treatment. Relative standardised incidence ratios and standardised mortality ratios for age at acquiring or dying from cervical or vaginal cancer (attained age), adjusted for preset variables.
Results: Women previously diagnosed with CIN3 had an increased risk of dying from invasive cervical or vaginal cancer, compared with the general female population (standardised mortality ratio 2.35, 95% confidence interval 2.11 to 2.61). After age 60 years, these women had an accelerated increased risk of acquiring invasive cancer; a similar steep increase in mortality risk was seen after age 70. Regression analyses indicated that the increase in risk over time is highly attributable to ageing.
Conclusions: Women previously treated for CIN3 are at increased risk of developing and dying from cervical or vaginal cancer, compared with the general female population. The risk accelerates above age 60 years, suggesting a need for lifelong surveillance of these women.