Authors: Gayathri Anandappa, Naureen Starling, Ruwaida Begum, Annette Bryant, Shruti Sharma, Derrick Renner, Maria Aresu, Clare Peckitt, Himanshu Sethi, Andrew Feber, Vanessa Alice Potter, Marius Paraoan, Muti Abulafi, Nicol George, Graham Branagan, Sarah Duff, Nicholas West, Alexey Aleshin, Ian Chau, David Cunningham,
Published: 2021-01-22
DOI: 10.1200/jco.2021.39.3_suppl.102
Source: Full article
102 Background: Numerous studies have shown the clinical utility of ctDNA, a non-invasive biomarker to detect MRD and stratify CRC patients who are more likely to relapse. We present an analysis of MRD detection in CRC patients from a prospective multicentre UK study, who were monitored pre- and post-surgery before adjuvant chemotherapy (ACT). Methods: The study recruited patients diagnosed with stage II-III CRC (n=122), including a subset of rectal patients who underwent tri-modality treatment (TMT). All patients had their primary tumor resected and 56% (68/122) received ACT. Paired plasma samples (n=244) were collected before surgery/neaodjuvant chemoradiotherapy and after surgery; median follow-up for survival was 15.48 months (0.16 - 42.1 months). Individual tumors and matched germline DNA were whole-exome sequenced and somatic single nucleotide variants (SNVs) identified. Multiplex PCR assays were designed to track tumor-specific SNVs (Signatera, bespoke mPCR NGS assay) in plasma samples. The study evaluated ctDNA status and clinical outcomes including radiologic imaging. Cox regression was used to calculate recurrence-free survival (RFS) in patients stratified by post-op ctDNA status. Patients were also stratified into low and high-risk groups based on the clinicopathological features. Multivariate analysis was performed with covariates: ctDNA, age, gender, laterality, stage, number of lymph node resected, MSI & TMB. Results: Pre-treatment ctDNA was detected in 93.4% (100/107) of patients. Post-operative ctDNA status prior to ACT was assessed in 107 patients, of whom, 13% (14/107) were MRD-positive (MRDpos). Of the MRDpos patients 42.9% (6/14) eventually relapsed. In contrast, only 8.6% (8/93) of MRD-negative (MRDneg) cases relapsed (HR: 10; 95% CI: 3.3-30; p<0.001). MRD rates stratified by risk features in each of the stages with respective recurrence rates are shown in Table. In stage III patients (n=64), 45.4% (5/11) of the MRDpos patients relapsed, whilst only 17% (9/53) of the MRDneg cases relapsed (HR: 9; 95% CI:2.6-32; p<0.0001). In the multivariate analysis, ctDNA status was the most significant prognostic factor associated with RFS (HR: 28.8, 95% CI: 3.5-234.1; p<0.001). Conclusions: Postoperative ctDNA analysis with tumor informed assay enables detection of CRC patients at high-risk of recurrence. Early detection of MRD could guide ACT decisions in intervention trials and is currently underway in TRACC. Clinical trial information: NCT04050345. [Table: see text]