Circulating Tumor DNA Dynamics and Clinical Outcomes in Patients with Advanced Colorectal Cancer Treated with...

We investigated whether circulating tumor DNA (ctDNA) changes may be useful to assess clinical outcomes in patients with metastatic colorectal cancer (mCRC) randomized in the TIME-PRODIGE-28 trial comparing biweekly maintenance with cetuximab alone with observation after 4-month fluorouracil, folinic acid, and irinotecan (FOLFIRI) plus cetuximab induction chemotherapy.

ctDNA samples were collected at four time points from baseline until disease progression during the first chemotherapy-free interval and analyzed using next-generation sequencing and methylation marker approaches. Progression-free survival (PFS) and overall survival (OS) from randomization were analyzed according to ctDNA kinetics and EGFR-MAPK pathway alterations.

Among 139 randomized patients, 104 (74.8%) had paired samples available. Patients with negative baseline ctDNA remaining negative after 4-month induction chemotherapy had significantly longer PFS from randomization (9.6 months) as compared with patients with a ctDNA decrease of ≥80% (3.4 months) or a ctDNA decrease of <80% (2.1 months; P = 0.013). Patients with EGFR-MAPK pathway alterations identified either in tissue or baseline ctDNA had worse PFS and OS from randomization. Acquired alterations found in 17 of 63 (26.9%) patients at disease progression during the first chemotherapy-free interval were associated with worse OS from reintroduction of the full induction chemotherapy (14.9 vs. 19.4 months; P = 0.025).

Our findings show the prognostic impact of both ctDNA kinetics and EGFR-MAPK pathway alteration dynamics following induction chemotherapy with FOLFIRI-cetuximab in patients with mCRC. Prospective studies evaluating ctDNA-guided treatment strategies are needed to validate the clinical utility of ctDNA monitoring to improve patient selection for first-line treatment de-escalation and anti-EGFR-based maintenance regimens, including treatment adaptation over time.