Clinical Application Of High-throughput Sequencing-based Liquid Biopsy In The Neoadjuvant Therapy Of Rectal Cancer

Background&Aims:Multiple approaches based on cell-free DNA(cfDNA)have been applied to detect minimal residual disease(MRD)and to predict prognosis or recurrence.The cfDNA-based biomarkers include mutations,copy number alterations(CNAs)and methylation,while mutation detection include individualized,multi-gene panel and other assays.However,a comparison of the approaches used in different cohorts and studies is difficult.Our aim was to compare multiple approaches for MRD analysis after neoadjuvant therapy(NAT)in patients with locally advanced rectal cancer(LARC).Designs:Sixty patients with LARC from a multicentre,phase Ⅱ/Ⅲ randomized trial were included,with tissue and blood samples collected.For each cfDNA sample,we profiled MRD using 3 approaches:personalized assay targeting tumor-informed mutations,universal panel of genes frequently mutated in colorectal cancer(CRC),and low depth sequencing for CNAs.Results:Positive MRD based on post-NAT personalized assay was significantly associated with an increased risk of recurrence(HR=27.38;log-rank P<0.0001).MRD analysis based on universal panel(HR=5.18;log-rank P=0.00086)and CNAs analysis(HR=9.24;log-rank P=0.00017)showed a compromised performance in predicting recurrence.Both the personalized assay and universal panel showed complementary pattern to CNAs analysis in detecting cases with recurrence and the combination of the two types of biomarkers may lead to better performance.Conclusions:The combination of mutation profiling and CNA profiling can improve the detection of MRD,which may help optimize the treatment strategies for patients with LARC.