Circulating Tumor DNA as a Prognostic Biomarker for Recurrence in Patients with Locoregional Esophagogastric Cancers with a Pathologic Complete Response

PURPOSEAfter neoadjuvant therapy (NAT) and surgery, up to one third and one half of patients with esophagogastric adenocarcinoma with a pathologic complete response (pCR; tumor regression grade 0 [TRG-0]) and near-pCR (TRG-1) will recur, respectively. Our study aims to evaluate postoperative circulating tumor DNA (ctDNA) as a predictor of recurrence in patients with pCR or near-pCR after curative-intent neoadjuvant chemotherapy or neoadjuvant chemoradiation and surgery.METHODSWe retrospectively identified patients from 11 institutions with stages I-IV esophagogastric cancers (EGCs) who completed NAT and had TRG-0/1 scores at the time of curative-intent surgery. Postoperative plasma samples were collected for ctDNA analysis within a 16-week molecular residual disease (MRD) window after definitive surgery, and during surveillance from January 7, 2020, to November 9, 2023, at the provider's discretion. ctDNA was assessed using a clinically validated, personalized, tumor-informed ctDNA assay (Signatera, Natera, Inc). The primary outcome was recurrence-free survival (RFS).RESULTSWe obtained 309 blood samples from 42 patients with esophagogastric adenocarcinoma with a pCR after neoadjuvant treatment over a median follow-up time of 28.5 months (range, 0.2-81.7). Detectable ctDNA in the 16-week MRD window (N = 23) correlated with higher rates of recurrence (67%; 2/3) compared with undetectable ctDNA (15%; 3/20). Detectable ctDNA within the MRD window was associated with a significantly shorter RFS (hazard ratio [HR], 6.2; P =.049). Among 32 patients who had ctDNA analyzed in the surveillance setting, the recurrence rate was 100% (5/5) in the ctDNA-positive cohort compared with 7.4% (2/27) in ctDNA-negative patients and was associated with shorter RFS (HR, 37.6; P <.001).CONCLUSIONWithin the subgroup of patients with EGC and favorable pathologic responses (TRG 0-1) after NAT, the presence of postoperative ctDNA identified patients with elevated recurrence risk.