Oncologic outcomes of endometrial cancer in patients with low-volume metastasis in the sentinel lymph nodes: An international multi-institutional study

Objective: To assess oncologic outcomes in endometrial cancer patients with low-volume metastasis (LVM) in the sentinel lymph nodes (SLNs). Methods: Patients with endometrial cancer and SLN-LVM (≤2 mm) from December 3, 2009, to December 31, 2018, were retrospectively identified from 22 centers worldwide. Patients with International Federation of Gynecology and Obstetrics (FIGO) stage IV, adnexal involvement, or unknown adjuvant therapy (ATx) were excluded. Results: Of 247 patients included, 132 had isolated tumor cell (ITC) and 115 had micrometastasis (MM). Overall 4-year recurrence-free survival (RFS) was 77.6% (95% CI, 70.2%–85.9%); median follow-up for patients without recurrence was 29.6 (interquartile range, 19.2–41.5) months. At multivariate analysis, Non-endometrioid (NE) (HR, 5.00; 95% CI, 2.50–9.99; P < .001), lymphovascular space invasion (LVSI) (HR, 3.26; 95% CI, 1.45–7.31; P = .004), and uterine serosal invasion (USI) (HR, 3.70; 95% CI, 1.44–9.54; P = .007) were independent predictors of recurrence. Among 47 endometrioid ITC patients without ATx, 4-year RFS was 82.6% (95% CI, 70.1%-97.2). Considering 18 ITC patients with endometrioid grade 1 disease, without LVSI, USI, or ATx, only 1 had recurrence (median follow-up, 24.8 months). Conclusions: In patients with SLN-LVM, NE, LVSI, and USI were independent risk factors for recurrence. Patients with any risk factor had poor prognosis, even when receiving ATx. Patients with ITC and grade 1 endometrioid disease (no LVSI/USI) had favorable prognosis, even without ATx. Further analysis (with more patients and longer follow-up) is needed to assess whether ATx can be withheld in this low-risk subgroup.