Increased survival in non-endometrioid endometrial cancer after introducing lymphadenectomy and tailoring radiotherapy - A population-based cohort study.

Objective: To investigate recurrence and survival in non-endometrioid endometrial cancer in a population-based cohort and evaluate the implementation of the first national guidelines (NGEC) recommending pelvic and paraaortic lymphadenectomy for surgical staging and tailored adjuvant therapy.

Methods: A population-based cohort study that used the Swedish quality registry for gynaecological cancer for the identification of all women with early-stage non-endometrioid endometrial cancer between 2010 and 2017. Five-year overall (OS) and disease-free survival (DFS) were calculated using the Kaplan-Meier method. The Cox proportional hazards regression model was used to evaluate the effect of age, FIGO stage, primary treatment and lymph node dissection on DFS.

Results: There were 228 patients included in the study cohort and 67 (29%) patients had a recurrence within five years. In the recurrence cohort, the OS was 13.4% (95%CI:7.3-24.7) compared to 88.5% (95%CI:83.4-93.9) if no recurrence occurred (log-rank p < 0.001). The DFS for the complete cohort was 61.9% (95%CI:55.7-68.7). The OS before implementation of NGEC was 57.3% (95%CI:48.2-68.1) and the DFS was 52.1% (95%CI:43.0-63.1) compared to an OS of 72.0% (95%CI:64.2-80.7; log-rank p = 0.018) and a DFS of 70.1% (95%CI:62.4-78.7; log-rank p = 0.008) after implementing NGEC. Patients received adjuvant radiotherapy in 92.7% before and 42.4% after NGEC implementation (p < 0.001). In the multivariable regression analysis, age, FIGO stage and lymph node dissection were found to be significant prognostic factors, where having a lymph node dissection decreased the risk of recurrence or death with a HR of 0.58 (95%CI:0.33-1.00).

Conclusion: In this population-based cohort of preoperative early-stage non-endometrioid EC, a significant improvement in survival was seen after NGEC implementation where lymph node staging for tailoring adjuvant therapy was introduced and less pelvic radiotherapy was given.