Clinical Significance of Soluble L1CAM Serum Levels in Patients with High-Risk Endometrial Cancer

Background/Objectives: Despite advances in targeted therapies, a substantial proportion of high-risk endometrial carcinomas (EC) do not respond to treatment and have a poor prognosis. The identification of prognostic and predictive biomarkers to improve patient stratification is therefore a clinical priority. L1 cell adhesion molecule (L1CAM) is a promising biomarker in EC; however, its soluble circulating form (sL1CAM) has been poorly investigated. This study aimed to evaluate the prognostic and predictive significance of sL1CAM in high-risk ECs. Methods: High-risk EC patients, treated with surgery and platinum-based adjuvant chemotherapy, were retrospectively enrolled. sL1CAM levels were quantified in 72 preoperative serum samples by enzyme-linked immunosorbent assay (ELISA). Results: High sL1CAM levels were associated with advanced age and non-endometrioid histology. Across the entire patient cohort, higher sL1CAM concentrations significantly correlated with worse prognosis in terms of DSS and PFS in univariate (DSS: HR = 2.22, p = 0.028; PFS: HR = 1.21, p = 0.041) and multivariate (DSS: HR = 2.13, p = 0.041; PFS: HR = 1.93, p = 0.048) analyses. Stratification by histological type revealed a significant prognostic association only in the endometrioid subgroup, both in univariate and multivariate analyses. Moreover, in this subgroup, elevated sL1CAM levels were associated with shorter time to recurrence after chemotherapy, both in univariate (PFI: HR = 2.69, p = 0.027) and multivariate (PFI: HR = 2.97, p = 0.017) analysis, and significantly predicted relapse within 6 months (OR = 7.83, p = 0.027). Conclusions: sL1CAM is associated with poor prognosis in high-risk EC and seems to be associated with platinum response in endometrioid tumors. These findings support its potential role as a biomarker to improve risk stratification, warranting validation in larger, prospective studies.