Circulating tumor DNA (ctDNA) trajectories predict survival in trifluridine/tipiracil-treated metastatic colorectal cancer patients.

Late-line treatment in metastatic colorectal cancer (mCRC) can improve prognosis. However, not every patient has a benefit and may experience severe side effects. Thus, predictive/prognostic biomarkers are urgently needed. We investigated the prognostic role of circulating tumor DNA (ctDNA) in mCRC patients before and during treatment with trifluridine/tipiracil (FTD/TPI). This noninterventional translational biomarker phase II study enrolled 30 mCRC patients (60% male, 40% female). Using a 77-gene panel, ctDNA was detectable in 90% of patients. Tumor levels were assessed based on aneuploidy (ichorCNA) as well as the highest variant allele frequency, and correlated with overall survival (OS). Uni- and multivariate survival analyses were performed with clinical variables. Longitudinal changes in tumor levels over time were analyzed with linear mixed and joint models. The median OS was 8.1 months, with a recorded disease control rate of 30%. High ctDNA levels (≥ 5%) were associated with inferior survival after undergoing FTD/TPI therapy. Elevated tumor level trajectories over time were associated with higher risks of death. Therefore, ctDNA can help identify patients who are unlikely to benefit significantly from this treatment in late-stage disease, thus preventing unnecessary treatments and their associated side effects, ultimately enhancing quality of life.