Clinical significance of isolated tumor cells and micrometastasis in low-grade, stage I endometrial cancer.

INTRODUCTION: Ultrastaging in endometrial cancer (EC) led to increased detection of isolated tumor cells (ITC, ≤0.2 mm) and micrometastases (MM, 0.2-2 mm), with unclear effect on prognosis. Our aim was to characterize the impact of ITC and MM on the outcome of these patients. METHODS: Grade 1 to 2 stage I endometrioid EC patients with nodal ITC (n = 11) or MM (n = 12) between 2012 and 2018 were retrospectively compared to a matched group of lymph node negative (n = 18) patients based on age, body mass index, grade, myometrial invasion, and lymphovascular space invasion (LVI) status using propensity score analysis (1:1). Mann-Whitney U tests were performed on continuous variables and χ2 tests on categorical variables. Progression-free survival (PFS) was the main endpoint. RESULTS: All MM and 81% of ITC had LVI. More ITC/MM patients received RT and chemotherapy (91.7% vs 18.4%; 70.8% vs 4.5%, respectively; P < 0.01) without significant difference in treatment-related toxicities (25% vs 27.3% grade 1%-2% and 20.8% vs 9.1% grade 2-3; P = 0.538) or PFS (29.2 vs 25 months; P = 0.828). Two distant recurrences occurred in MM patients after 2.5 years; one lung and one para-aortic lymph node. CONCLUSION: With adjuvant treatment, ITC/MM in otherwise well-differentiated stage I endometrial cancer have similar outcomes to matched LN- patients.