The 10-year results after national introduction of pelvic lymph node staging in Danish intermediate-risk endometrial cancer patients not given postoperative radiotherapy. Gitte Ørtoft; Claus Høgdall; Estrid S Hansen; Margit Dueholm. Objective: To prepare for the national introduction of sentinel node staging, we evaluated the consequences of the previous national decision to introduce lymph node staging in intermediate-risk endometrial cancer patients (grade 1/2 with > 50% or grade 3 with < 50% myometrial invasion) by determining the number of patients upstaged by lymphadenectomy and whether upstaging affected the survival and recurrence patterns of non-staged patients and patients with and without lymph node metastases. Study Design: In a national cohort study, 2005–12, 1294 stage I–IV patients who should have been offered lymphadenectomy were progressively registered. The number of patients upstaged by lymphadenectomy, 10-year survivals were evaluated by Kaplan–Meier analysis and adjusted Cox regression. Results: This study demonstrates that it takes time to introduce lymphadenectomy at a national level, as indicated by the increasing number of cases staged per year, from 12% in 2005 to 74% in 2012. Pelvic lymphadenectomy was performed in 43.8% (567/1294) and lymph node metastases were found in 13.6% (77/567). As 54 patients had further dissemination outside the uterine body, only 23 patients (6%) were upstaged from stage I to IIIC. Compared to lymph node-negative patients, the 77 patients with lymph node metastasis had significantly lower overall, (55% versus 68%), disease-specific (64% versus 86%), and progression-free survival (51% versus 77%), mainly due to non-local recurrences including a high number of paraaortic recurrences. In 873 final stage I intermediate-risk patients, 10-year survival and recurrence rates were not significantly lower in non-staged as compared to lymph node-negative patients (overall survival 62% versus 70%: disease-specific survival: 90% versus 90%, progression-free survival: 81% vs 83%), probably due to the low number of patients upstaged from stage I to stage IIIC. Conclusion: Lymph node metastases were present in 13.6% of patients with intermediate-risk who underwent pelvic lympadenectomy, and these patients had a lower 10-year survival than lymph node-negative patients. Because lymphadenectomy upstaged only 6% from stage I to stage IIIC, survival and recurrence rates were not significantly compromised in non-staged as compared to lymph node-negative intermediate-risk stage I patients. Sentinel node staging has now been implemented in Danish intermediate-risk endometrial cancer patients.