IMMUNOHISTOCHEMICAL BIOMARKERS IN EC 113 5 Lymph node status For LN status three subgroups were defined: histologically confirmed LNM (N1), LN sampled by lymphadenectomy and histologically negative (N0), and LN status unknown (Nx) if no lymphadenectomy was performed. Sentinel lymph node (SLN) procedure was allowed but not performed in this study cohort. For the relation of IHC biomarkers and LN status, including the survival analysis, patients with LN status unknown (Nx) were excluded for analysis. Outcome measurements Our primary aim was to define the added prognostic relevance of preoperative IHC biomarkers, p53/L1CAM/ER/PR, to the ESMO-ESGO-ESTRO risk classification groups in EC. Secondary, the added prognostic relevance of these IHC biomarkers to LN status in EC. Statistical analysis For statistical analyses, Statistical Package for the Social Sciences (SPSS), version 25.0 (IBM, New York, NY, USA) was applied. The results were considered significant if P-value was less than 0.05 (P<0.05). For the association of IHC expression with the ESMO-ESGOESTRO risk classification groups, the Mantel-Haenszel chi2 test for trend was used. Survival analyses were performed using the Kaplan Meier curves (first 10 years after diagnosis) and univariate and multivariate Cox-regression. Recurrence-free survival (RFS) was defined as time from surgery to time of recurrence from EC disease, and disease-specific survival (DSS) was defined as time from date of surgery to date of death from EC, all censored by date of last contact. The definition of ER/PR was defined as either ER or PR negative and/or positive. The ESMO-ESGO-ESTRO risk classification in the survival analysis was dichotomized: ‘low, intermediate and high-intermediate’ and ‘high and advanced/metastatic’. This dichotomy was used, as the ‘high and advanced/metastatic’ ESMO-ESGO-ESTRO risk classification groups included all cases with LNM. Associations were calculated as hazard ratio (HR) with corresponding 95% confidence interval (CI) and P-value. RESULTS Study cohort A total of 1199 patients were included from ten European hospitals. For the current study only patients with available preoperative endometrial biopsies were included. Samples with insufficient tumor tissue were excluded, resulting in 763 patients with a median followup of 5.5 years9. Baseline patient- and tumor characteristics of included patients were not significantly different when compared with excluded patients (data not shown).
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