Whole Exome Sequencing of Low Risk Endometrial Cancer Patients with Isolated Local Recurrences

A small proportion of clinicopathologically low-risk endometrial cancer (EC) patients who omitted adjuvant radiotherapy (RT) may subsequently develop a local recurrence. Molecular profile for those clinically low-risk yet recurred EC patients is unavailable. A total of 442 EC patients treated from 2014 to 2020 at Northwestern Memorial Hospital were studied. Among them, 28 patients clinically low risk or low-intermediate risk per GOG-99 criteria developed an isolated local recurrence after hysterectomy, bilateral salpingo-oophorectomy, and omitted RT. Whole exome sequencing (WES) was performed on 22 patients whose pathologic specimen were retrievable. The majority of the cases studied were molecularly No Specific Molecular Profile (NSMP) cohort (91%). We identified CTNNB1, FGFR2, PTEN, and KRAS as the most frequently altered pathogenic or likely pathogenic genes with 5 (22.7%), 5 (22.7%), 4 (18.2%), and 3 (13.6%) out of 22 patients carrying these alterations, respectively. TP53 somatic alterations were identified in 2 (9.1%) out of 22 cases. Analysis of The Cancer Genome Atlas Uterine Corpus Endometrial Carcinoma (TCGA-UCEC) dataset identified 53 EC patients with pathologically Grade 1 molecularly NSMP cohort. Within this cohort, CTNNB1 alterations were identified in 31 patients (58%) and prognosticated worse progression free survival (p<0.05). NSMP molecular group constitutes the majority of clinically low-risk EC patients with isolated local recurrences. The CTNNB1 alteration was validated as a biomarker in prognostication in this independent cohort and may help guide adjuvant treatment decisions.