Identification of a very-high risk subgroup of localized endometrial carcinoma before surgery using circulating tumor DNA: a proof-of-concept study.

Objective: We aimed to study whether the detection of circulating tumor DNA (ctDNA) may predict the risk of early relapse for patients with localized endometrial carcinoma.

Methods: Patients who underwent surgical resection at Cochin University Hospital (2021-2023) for International Federation of Gynecology and Obstetrics 2018 stage I to III endometrial carcinoma were prospectively included in a prospective biocollection cohort study. All patients had a plasma sample before surgery (EDTA collection tubes, 4-5 mL). After extraction and bisulfite-conversion of cell-free DNA, ctDNA was evaluated using a droplet-digital polymerase chain reaction assay targeting universally-hypermethylated positions in endometrial carcinoma (OXT, ZSCAN12 genes), and defined as significantly detected above the limit of detection. Patients were classified as high-risk based on 2022 European Society for Medical Oncology/European Society of Gynaecological Oncology/European Society of Pathology guidelines, or preoperative features (non-endometrioid histology, p53-abnormal tumors, or stage III). Events of interest were tumor progression or relapse (event-free survival). Adjusted-HR (aHR) was estimated using Cox regression.

Results: Among 128 patients included with median follow-up of 26 months (interquartile range; 15-35), ctDNA was detected in 18 patients (14%). Patients with ctDNA had a 1-year event-free rate of 67% (95% CI [48% to 92%]), vs 91% [82% to 100%] among patients without ctDNA. The ctDNA was detected in 10 (29%) patients among those with preoperative high-risk features (N = 34, 1-year event-free rate = 60% [36%-100%]). ctDNA was associated with event-free survival independently of stage (aHR = 4.26 [1.68-10.8]), 2022 guidelines high-risk (aHR = 3.72 [1.57-8.87]), or preoperative high-risk features (aHR = 3.98 [1.65-9.60]).

Conclusions: Elevated ctDNA before surgery identifies a very high-risk subgroup of newly diagnosed endometrial carcinoma, suggestive of occult metastasis. Further studies are warranted to validate this finding and investigate the window of opportunity for neoadjuvant approaches.