Prognostic Effect of Mismatch Repair Status in Early-Stage Endometrial Cancer Treated With Adjuvant Radiation: A Multi-institutional Analysis

Purpose: The aim of this work was to report the effect of mismatch repair (MMR) status on outcomes of patients with stage I -II endometrioid endometrial adenocarcinoma (EEC) who receive adjuvant radiation therapy. Methods and Materials: This is a multi -institutional retrospective cohort study across 11 institutions in North America. Patients with known MMR status and stage I -II EEC status postsurgical staging were included. Overall survival (OS) and recurrence -free survival (RFS) rates were estimated via the Kaplan -Meier method. Univariable and multivariable analyses were performed via Cox proportional hazard models for RFS and OS. Statistical analyses were conducted using SPSS version 27. Results: In total, 744 patients with a median age at diagnosis of 65 years (IQR, 58-71) were included. Most patients were White (69.4%) and had Federation of Obstetrics and Gynecology 2009 stage I (84%) and Federation of Obstetrics and Gynecology grade 1 to 2 (73%). MMR de fi ciency was reported in 234 patients (31.5%), whereas 510 patients (68.5%) had preserved MMR. External beam radiation therapy with or without vaginal brachytherapy was delivered to 186 patients (25%), whereas 558 patients (75%) received vaginal brachytherapy alone. At a median follow-up of 43.5 months, the estimated crude OS and RFS rates for the entire cohort were 92.5% and 84%, respectively. MMR status was signi fi cantly correlated with RFS. RFS was inferior for MMR de fi ciency compared with preserved MMR (74.3% vs 88.6%, P < .001). However, no difference in OS was seen (90.8% vs 93.2%, P = .5). On multivariable analysis, MMR de fi ciency status was associated with worse RFS (hazard ratio, 1.86; P = .001) but not OS. Conclusions: MMR status was independently associated with RFS but not OS in patients with early -stage EEC who were treated with adjuvant radiation therapy. These fi ndings suggest that differential approaches to surveillance and/or treatment based on MMR status could be warranted. (c) 2024 Elsevier Inc. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)