The Progression of Vaginal Intraepithelial Neoplasia to Cancer: A Systematic Review and Meta-Analysis

Objectives: This study aimed to better estimate the risk of progression of vaginal intraepithelial neoplasia (VaIN) into vaginal cancer. Method: A systematic review was conducted to identify eligible studies that (1) reported at least one event of progression from VaIN to vaginal cancer, (2) provided the VaIN grade, (3) had a follow-up period of at least 6 months, and (4) specified the proportion of treated and untreated patients. The effect size was the risk of progression from VaIN to invasive cancer, calculated as the number of events of progression out of all the observed cases at enrolment. Results: Five thousand seven hundred and sixty-eight references were screened; 30 case series were deemed eligible for qualitative analysis. Twenty case series of treated women, and four case series of untreated women were quantitatively analyzed. Both subgroups included cases of high-grade VaINs (no progressions to vaginal cancer found in low-risk VaINs). A sensitivity analysis on the subgroup of untreated women resulted in the exclusion of a study with excessive influence, with the final data synthesis based on three poor-quality case series. The risk of progression of high-grade VaIN to vaginal cancer in treated women was 7.09% (95% confidence interval [CI]: 6.83-7.36%). The risk of progression of high-grade VaIN to vaginal cancer in untreated women was 29.88% (95% CI: 11.22-58.96%). Progression events primarily occurred within 5 years of follow-up. Conclusion: The risk of progression of high-grade VaIN to vaginal cancer is higher than previously reported and more serious for untreated women (CRD42024618227).