Abstract 5118: Postoperative minimal residual disease to predict the risk of hepatocellular carcinoma (HCC) recurrence using plasma-only circulating tumor DNA assay
Authors: Pan Mingxin , Cai Jianpeng , Xu Yuyan , Zhong Kaihang , Chen Tingting 
Published: June 2022

Abstract
Background: Postoperative minimal residual diseases (MRD) are one of the main causes of postoperative short-term recurrence, which were difficult to be detected by conventional imaging examinations. Circulating tumor DNA (ctDNA) provides a novel approach for detecting the existence of MRD and predicting clinical outcomes of hepatocellular carcinoma (HCC). Most ctDNA MRD assays require tumor sequencing to identify tumor-derived mutations to facilitate ctDNA detection, requiring tumor and blood. Herein, we evaluated a plasma-only ctDNA assay integrating genomic signatures to enable tumor-uninformed MRD detection. Methods: 20 patients with hepatocellular carcinoma who underwent radical surgical resection were involved from July 2019 to October 2020. Blood samples were collected for next generation sequencing (NGS) within 7 days after surgery, and 10 of them had preoperatively matched plasma ctDNA results. NGS (381 genes panel) was performed on plasma samples to capture tumor somatic single-nucleotide variants (SNVs) and copy number variants (CNVs). Clinical information was obtained to evaluate the prognostic performance of ctDNA comparing with traditional clinical biomarkers. Plasma and peripheral blood cell samples were sequenced to a mean depth of 7396 and ctDNA results correlated with recurrence-free survival (RFS). Results: Characteristics of the 20 HCC patients were as follows: 85% age≥50 years, 70% HBV positive, 75% largest tumor diameter≥5cm, 55% liver cirrhosis, 85% AFP &gt; 400ng/ml, 60% MVI, 55% PVTT, 50% BCLC C, 70% CNLC III. After a median follow-up of 13.60 months, 10 recurrence events were recorded. In order to evaluate the presence of MRD after radical surgery, at least one low frequency SNV detected was considered ctDNA-positive. Using stringent quality criteria 8/20 (20%) were ctDNA positive after resection. The median RFS for ctDNA-positive patients was 6.98 months versus 27.57 months for ctDNA-negative patients (HR 3.727, 95% CI 0.9461-14.65; p=0.0247). Combining postoperative ctDNA SNV and preoperatively ctDNA CNV features could increase the sensitivity for predicting prognosis. To further confirm the effect of MRD on the RFS of HCC patients, multiple Cox regression was used to assess the effect of multiple factors, including MRD, alpha-fetoprotein (AFP), HBV, Liver cirrhosis, macrovascular invasion, PVTT, Child-Pugh score and CNLC stage, on the RFS. The forest plot results showed that the postoperative ctDNA was an independent factor for predicting the RFS of patients with HCC (MRD: HR=14.02, p=0.018). Conclusion: These preliminary results suggest that ultra-deep sequencing of ctDNA analyses can detect somatic mutations to reflect postoperative MRD state and predict recurrence of HCC. Plasma-only MRD detection may be an effective and convenient approach for clinical prediction of HCC postoperative recurrence risk.
Citation Format: Mingxin Pan, Jianpeng Cai, Yuyan Xu, Kaihang Zhong, Tingting Chen. Postoperative minimal residual disease to predict the risk of hepatocellular carcinoma (HCC) recurrence using plasma-only circulating tumor DNA assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5118.