4.2 Strengths and limitations
The main strength of this study is that it is the largest to date to compare IU with non-IU manipulators in a homogeneous cohort of patients with early-stage, low-grade EEC. The study’s nationwide multicentre design and 10-year inclusion period contributed to its large sample size (N = 5,205), which substantially increased the statistical power and allowed robust analysis. Moreover, the median follow-up period of 64 months was relatively long. This provided a higher chance of detecting differences in recurrence and survival, as most recurrences occur during the first two years after initial treatment21,22.
The current work has some drawbacks, including its retrospective nature. Our study population was categorized according to hospital manipulator preference, as data extraction on manipulator use at patient level was not feasible. Obtaining data on hospital manipulator preference through a survey appeared challenging, as it was not always documented well which uterine manipulators were used over the years. However, we addressed this by contacting hospitals with questionable survey answers for further clarification and, therefore, do not expect this to influence the current results. Another limitation is the variability in other treatment practices across hospitals, including the surgical procedure and systemic therapy indications. However, these variations reflect clinical practice and make our findings more applicable. Also, early-stage, low-grade EEC is normally not an indication for an academic referral. It could be that a part of the patients was treated in academic hospitals because of e.g., severe co-morbidity or high BMI, which may have influenced our results.