The prognostic value of circulating in blood tumor DNA as a marker of minimal residual disease in stage I–III colorectal cancer

Abstract

Introduction. Studies on non-metastatic colorectal cancer have demonstrated the prognostic role of circulating tumor (ctDNA) after surgery, and the ability to identify patients with the greatest risk of progression. This makes it possible in the future to personalize neoadjuvant and adjuvant treatment.The study objective – to evaluate the correlation of the ctDNA status before and after surgery with a clinical outcome in patients with stage I–III colorectal cancer.Materials and methods. The study included data from patients with morphologically verified colorectal cancer with stage I–III who were treated at the N. N. Blokhin National Oncology Research Center in the period from 2016 to 2021. Blood samples were collected before and after surgical treatment (on the 7–10th day after surgery). The minimum permissible concentration at which ctDNA in a plasma sample was considered positive was 0.4 copies of mutant DNA in 1 mcL of plasma. The main criterion of effectiveness was disease-free survival (DFS). The presence of cDNA before and after surgery was a negative prognostic factor for progression in stage I–III of CRC. Patients with positive cDNA after surgery had worse DFS results despite adjuvant chemotherapy. Patients with stage II CRC with negative ctDNA, regardless of adjuvant CT after surgery, did not have disease progression in 100 % of cases.Results. The study included 146 patients with stage I–III colorectal cancer. Progression was detected in 34 patients. The median follow-up time was 22 months (0–66 months). Data on progression were known in 119 patients. Positive cDNA data were detected before surgery in 55 of 120 patients (45 %), after surgery in 46 of 119 (38.6 %). In the group with positive cDNA before surgery, the median DFS was 35 months (95 % confidence interval (CI) 24,0–45.9), in the group with negative cDNA before surgery, the median DFS was not achieved (hazard ratio (HR) 4.6; 95 % CI 2.0–10.4), 1‑year DFS in the cDNA positive group was 62 % versus 100 % in the cDNA negative group (p <0.001). In the group with positive cDNA after surgery, the median DFS was 20 months (95 % CI 8,1–31,9), in the group with negative cDNA was not achieved (HR 27,7; 95 % CI 6,6–116,6; p <0,001). Patients with positive cDNA after surgery had worse DFS scores despite adjuvant chemotherapy. Patients with stage II CRC without ctDNA after surgery in 100 % did not have disease progression regardless of adjuvant CT.Conclusion. The presence of cDNA before and after surgery was a negative prognostic factor of progression after surgical treatment at stage I–III. The high negative prognostic value of cDNA makes it possible to select patients with stage II who do not need adjuvant chemotherapy.