The effectiveness of CIN treatments in preventing invasive cervical cancer has been suggested to be up to 99%, but several studies have shown the incidence of cervical cancer to still be elevated after treatment of CIN and the increased risk to last up to 20 years.
The mean age of women treated for CIN is very similar to with the mean age of first pregnancy in developed countries and the treatment of CIN has been associated with to an increased risk of preterm birth and perinatal morbidity in subsequent pregnancies. Furthermore, the radicality of the treatment has been shown to modify the effect of conization to reproductive morbidity.
Due to the ongoing debate regarding the risk and benefits associated with optimal treatment and follow-up strategies of CIN, our aim was to comprehensively assess the incidence of cervical and other cancers after treatment of CIN and the incidence of related reproductive morbidity by performing a series of systematic reviews and meta-analysis of the literature — regarding the invasive cancer incidence, and the reproductive morbidity after treatment of CIN correlated with the radicality of the treatment.
We searched electronic databases for studies reporting on cervical cancer incidence or mortality, preterm birth, and related outcomes after local, either ablative or excisional, treatment of CIN. Independent reviewers extracted the data and performed quality assessment for cancer incidence and reproductive morbidity outcomes separately. Pooled risk ratios were calculated with a random effects models. Inter-study heterogeneity was assessed with I2 statistics.
Treatment of CIN increases the risk of subsequent preterm birth. Increasing radicality of the treatment, measured as the depth of the cone removed, is associated with higher risk of preterm birth. On the other hand, incidence of cervical cancer, as well as of other HPV-related cancers is increased after treatment of CIN despite a marked effect in cancer prevention.
To ensure optimal cancer preventive effect with minimal collateral harm, especially reproductive morbidity, we would need to compare the absolute risks and the effects the treatments have on them regarding both invasive cervical cancer incidence and preterm birth incidence — in different populations, and stratified according to radicality of the treatment.