Substantial as opposed to focal or no lymphovascular space invasion (LVSI) is proposed as an independent adverse prognostic factor in patients with early-stage endometrioid endometrial cancer (EEC). We reviewed outcomes of patients treated with adjuvant vaginal brachytherapy (VB) alone in a single institution, stratified by LVSI extent.

Retrospective review identified Stage I-II EEC patients receiving VB alone from 2010 to 2017. Extent of LVSI was reported as none, focal, or substantial. Kaplan-Meier estimates and Log-Rank test were used to determine significance between variables. Cox proportional hazards model was used for multivariate analyses.

In total, 325 patients were identified with a median follow-up of 35 (23-48) months. LVSI was found in 112 patients with extent reported in 78, 45 (58%) had focal, and 33 (42%) substantial LVSI. Estimated disease-free survival for those with substantial LVSI was 73 (57-94)%, focal LVSI 89 (79-100)%, and no LVSI 94 (90-98)% at 48 months (p = 0.012). On multivariate analyses substantial LVSI was the only risk factor predictive of pelvic [HR substantial vs no: 7.2 (1.0-51.6); p = 0.048] and distant failure [HR substantial vs no: 4.4 (1.2-16.3); p = 0.027]. Both high-grade disease [HR 3 vs 1: 5.5 (1.2-25.6); p = 0.031] and extent of LVSI [HR substantial vs no: 4.4 (1.7-11.4); p = 0.002] predicted for worse disease-free survival.

Substantial LVSI was the strongest adverse prognostic factor for pelvic and distant failure in this cohort of EEC patients receiving adjuvant VB alone, suggesting this subset may benefit from additional adjuvant therapy. This study underscores the importance of quantifying LVSI extent in EEC.