SLYMEC II study: Overall survival analysis of the impact of LVSI in apparent early stage endometrioid endometrial cancer

Abstract
In our initial report of the SLYMEC study we published the results evaluated the prognostic impact of substantial lymphovascular space invasion (LVSI) on the sentinel lymph node status and the impact of the different types of LVSI on 3-year disease-free survival.
The aim of the SLYMEC II study was to assess the impact of focal and substantial lymphovascular space invasion on 5-years overall survival in the subgroup of patients with endometrioid endometrial cancer. A total of 2030 patients were included in the analysis from the original data set. Focal LVSI were identified in 131 patients (6.4 %), whereas 319 patients (15.7 %) showed substantial LVSI at final pathology. Among 1876 patients who underwent minimally invasive surgery (92.6 %), 442 patents (21.8 %) underwent robotic assisted surgery, whereas and 150 patients (7.6 %) patients underwent open surgery. Rate of overall survival at 5 years was 83.6 % versus 100 % for substantial and focal LVSI groups, respectively (HR for death = 2.1 [95 % CI, 1.4 to 3.2]; P < 0.0001). Patients with endometrioid endometrial cancer having substantial LVSI after surgery showed an increased risk of death in the after 5-years overall survival when compared to patients with negative, or focal LVSI. The presence of positive LVSI in patients with positive sentinel nodes showed a trend toward reduced 5-year overall survival compared to SLN-negative patients, although it did not reach statistical significance.
Introduction
The presence of lymphovascular space invasion (LVSI), defined as the presence of tumor emboli in the endothelial-lined space within the myometrium beyond the invasive front of the tumor, represents one of the most important prognostic factors in the management of women with endometrial cancer. By adopting the WHO definition [1], a focal lymphovascular invasion can be defined when 1 to 4 vessels involved on at least one pathology slide, whereas a substantial lymphovascular invasion is diagnosed when 5 or more vessels are involved on at least one pathology slide. In the recent update of the FIGO classification, the presence of LVSI was integrated as a risk factor by adopting the WHO definition for substantial LVSI [2]. Nevertheless, data from the literature are heterogeneous and discordant. Peters et al., highlights how urgent it is to standardize the definition of LVSI [3]. Recently, a large study of the Memorial Sloan Kettering Cancer Center, showed that focal LVSI have a negative impact on prognosis of women with stage IA and IB endometrioid endometrial cancer [4]. The aim of this study was to explore the impact of the different types of LVSI on the overall survival outcome in the subgroup of patients with endometrioid endometrial cancer extracted from dataset of the SLYMEC study [5]. In addition, we evaluated the progression-free survival at 5 years, as well as a long-term analysis of the impact of LVSI based on the sentinel lymph node status.