Myometrial invasion and tumor free distance from serosa as prognostic factors in endometrial endometrioid carcinoma

OBJECTIVE: Our aim was to investigate the prognostic role of myometrial invasion (MI) and tumor free distance (TFD) from serosa in patients with endometrial endometrioid carcinoma (EEC). METHODS: In this retrospective multicenter study patients diagnosed with EEC with MI ≥50% were enrolled and treated at Policlinico Monserrato (Cagliari) and San Raffaele (Milan) from January 2016 to June 2023, with at least one year follow up. Youden index was determined for stratification, obtaining as cut off 82.5% for MI and 3 mm for TFD. Subgroups were related to lymph node (LN) status, grading, lymph vascular space involvement (LVSI), recurrence and survival. RESULTS: Overall, 127 patients were included; 20 (15.7%) had positive LN; 20 (15.7%) relapsed. Considering 82.5% as cut off for MI, 68 patients (53.5%) had MI <82.5%, 59 (46.5%) ≥82.5%. Considering 3 mm as cut off for TFD, 64 patients (50.4%) had TFD ≥3 mm, 63 (49.6%) <3 mm. At multivariate analysis, MI ≥82.5% was associated with LN metastases (p=0.002) and recurrence (p=0.019); TFD <3 mm was related to recurrence (p=0.003), especially at distant sites, but not LN metastases (p=0.100). MI and TFD retained significance for disease free survival (DFS) alone (p=0.039 and p=0.007, respectively) and in combination (p=0.041). CONCLUSION: MI and TFD represent crucial prognostic factors for recurrence, DFS and LN metastases, also providing information about recurrence site. Further studies are required to evaluate their role.