Prognostic value of isolated tumor cells in sentinel lymph nodes in low risk endometrial cancer: Results from an international multi-institutional study

Objective: The prognostic significance of isolated tumor cells (≤0.2 mm) in sentinel lymph nodes (SLNs) of endometrial cancer patients is still unclear. Our aim was to assess the prognostic value of isolated tumor cells in patients with low risk endometrial cancer who underwent SLN biopsy and did not receive adjuvant therapy. Outcomes were compared with node negative patients. Methods: Patients with SLNs-isolated tumor cells between 2013 and 2019 were identified from 15 centers worldwide, while SLN negative patients were identified from Mayo Clinic, Rochester, between 2013 and 2018. Only low risk patients (stage IA, endometrioid histology, grade 1 or 2) who did not receive any adjuvant therapy were included. Primary outcomes were recurrence free, non-vaginal recurrence free, and overall survival, evaluated with Kaplan-Meier methods. Results: 494 patients (42 isolated tumor cells and 452 node negative) were included. There were 21 (4.3%) recurrences (5 SLNs-isolated tumor cells, 16 node negative); recurrence was vaginal in six patients (1 isolated tumor cells, 5 node negative), and non-vaginal in 15 (4 isolated tumor cells, 11 node negative). Median follow-up among those without recurrence was 2.3 years (interquartile range (IQR) 1.1-3.0) and 2.6 years (IQR 0.6-4.2) in the SLN-isolated tumor cell and node negative patients, respectively. The presence of SLNs-isolated tumor cells, lymphovascular space invasion, and International Federation of Obstetrics and Gynecology (FIGO) grade 2 were significant risk factors for recurrence on univariate analysis. SLN-isolated tumor cell patients had worse recurrence free survival (p<0.01) and non-vaginal recurrence free survival (p<0.01) compared with node negative patients. Similar results were observed in the subgroup of patients without lymphovascular space invasion (n=480). There was no difference in overall survival between the two cohorts in the full sample and the subset excluding patients with lymphovascular space invasion. Conclusions: Patients with SLNs-isolated tumor cells and low risk profile, without adjuvant therapy, had a significantly worse recurrence free survival compared with node negative patients with similar risk factors, after adjusting for grade and excluding patients with lymphovascular space invasion. However, the presence of SLNs-isolated tumor cells was not associated with worse overall survival.