The historical MoMaTEC1 outcome data, collected from 2001-2015 serve as control arm. These data have been rigorously collected and quality controlled with extensive clinical annotation and follow-up data, and reflect the outcome in (for a larger part) the same population as expected for MoMaTEC2 as there have not been major changes in surgical or medical treatment for endometrial cancer in this time period that could cause confounding. Internal validity, and to a degree also external validity, covering practice in multiple countries, should in this way be assured.

For the current study, stathmin is used as an integrated marker and does not dictate treatment modality, therefore there is no requirement for a control arm.

Lymphadenectomy in the pelvis and para-aortic, will, for patients who are considered otherwise low risk (endometrioid tumours grade 1 or 2, or grade 3 with <50% myometrial infiltration (MI), with no sign of extrauterine disease), be dependent on the preoperative hormone receptor status (ER and PR).

Patients will be defined low risk when endometrioid, grade 1 or 2, or grade 3 with <50% MI, AND positive hormone receptor status for both ER AND PR. These patients will not undergo lymphadenectomy.

Patients with endometrioid tumours grade 1 or 2, or grade 3 <50% MI,, with either negative ER or PR status, are defined high risk and will undergo pelvic and para-aortic lymphadenectomy as part of their surgical procedure.

Patients will receive routine clinical follow-up for 5 years. Follow-up data will be collected for the study, focusing on survival and recurrence of disease. All patients will, as part of the study fill out validated quality of life questionnaires (QoL) at follow-up.

The percentage of lymphadenectomy can be reduced safely and significantly, from 70% (MoMaTEC1 study results) to 30% in the MoMaTEC2 study through a better risk stratification of patients, especially better identification of low risk patients. Additionally The percentage of patients who need to be subjected to adjuvant (chemo) therapy can be reduced similarly from 20 to 10%, based on the same, optimised risk stratification and better identification of low risk patients. Patients will be rigorously followed during 5 years to detect any unexpected increase in the percentage of patients suffering a recurrence compared to the historical MoMaTEC1 cohort.

stathmin level will be measured in metastatic tissue and related to response to treatment using Response Evaluation Criteria In Solid Tumors (RECIST) criteria

Quality of life will be measured through validated questionnaires (EORTC QLQ-C30 and EORTC QLQ-EN24).