Introduction Surgical staging of endometrial cancer (EC) serves to allocate women with lymph node metastases to adjuvant treatment. Sentinel lymph node (SLN) mapping can accurately detect lymph node metastases in women with EC of low- or intermediate-risk (LR or IR) of lymph node metastases. We aim to investigate risks and benefits of a national protocolled adoption of SLN mapping to women with LR and IR EC, in a real-life clinical setting.

Methods A national multicenter prospective study of SLN-mapping in women with LR and IR EC from March 2017-February 2022. Postoperative complications were classified according to Clavien-Dindo. Lymphoedema was evaluated by validated patient-reported outcome measures at baseline and three months postoperatively.

Results 627 women were included in the analyses, 458 with LR- and 169 with IR EC. The SLN detection rate was 94.3% (591/627). The overall incidence of lymph node metastases was 9.3% (58/627), 4.4% (20/458) in the LR- and 22.5% (38/169) in the IR group. Only 0.3% (2/627) experienced an intraoperative complication associated with the SLN procedure. The incidence of postoperative complications was 8% (50/627). The mean difference score of lymphoedema was below the threshold for clinical importance 4.3/100 (95%CI 2.6–5.9). The incidence of leg swelling and heaviness was low, 5.2% and 6.1%, respectively.

Conclusion/Implications SLN mapping is a safe staging procedure in women with EC of LR and IR, carrying a very low risk of early lymphoedema, perioperative- and postoperative complications. The change in clinical practice contributed to improved treatment allocation for both risk groups and thus supports further international implementation.