2.2 Data collection
Patients were identified from the Netherlands Cancer Registry (NCR),
which is a population-based registry with coverage of all newly
diagnosed malignancies in the Netherlands since 1989. Dedicated
registration clerks routinely extract patient information from medical
records within the hospitals. Information on vital status and date of
death were obtained from the municipal demography
registries18. The NCR database was linked with patient
files in the Pathological Anatomical National Automated Archive (PALGA),
which is a national histo- and cytopathology register that archives all
pathology reports in the Netherlands19. Patients’ age
at time of diagnosis, treatment information, final surgery
histopathology, and follow-up data were obtained for each patient.
Treatment information consisted of date of surgery, type of surgery
(e.g., with or without BSO), details about the hospital at which surgery
was performed, and information regarding adjuvant treatment (e.g.,
radiotherapy, chemotherapy, hormone therapy). Final surgery
histopathology data collected were histotype according to the
International Classification of Diseases for Oncology (ICD-O),
differentiation grade, FIGO stage 200920, maximum
tumour diameter and presence of LVSI. Follow-up data was available on
histologically confirmed recurrence of cancer, including date and site
of recurrence, vital status, and date of death. In case of incoherent
data, the PALGA histopathology records were leading for histotype and
differentiation grade, and the NCR database was leading for disease
stage.
National hospitals were contacted to retrieve data regarding hospital
manipulator preference (i.e., IU or non-IU manipulator) between 2010 and
2020 by means of an online survey. The survey was formatted via
Microsoft Forms and distributed to the appointed representative, a
gynaecologist who performs minimally invasive hysterectomy for
endometrial cancer, of each national hospital. Questions included in the
survey are displayed in Table S1. In the absence of response, reminder
emails were sent to those hospitals. Hospitals with disputable responses
were contacted again for further clarification (by means of a phone call
or an email). If the manipulator preference within a hospital changed
between 2010 and 2020, these hospitals were analysed as independent
institutions before and after the date of change in manipulator
preference. Hospitals that used both IU and non-IU manipulators
simultaneously between 2010 and 2020 and their corresponding patients
were excluded from the analysis, as patients were categorized into IU
group and non-IU group according to hospital manipulator preference
rather than manipulator use at patient level.