No abstract

Circulating tumor DNA (ctDNA) has emerged as a biomarker with wide-ranging applications in cancer management. While its role in guiding precision medicine in certain tumors via noninvasive detection of susceptibility and resistance alterations is now well established, recent evidence has pointed to more generalizable use in treatment monitoring. Quantitative changes in ctDNA levels over time (i.e., ctDNA kinetics) have shown potential as an early indicator of therapeutic efficacy and could enable treatment adaptation. However, ctDNA kinetics are complex and heterogeneous, affected by tumor biology, host physiology, and treatment factors. This review outlines the current preclinical and clinical knowledge of ctDNA kinetics in cancer and how early on-treatment changes in ctDNA levels could be applied in clinical research to collect evidence to support implementation in daily practice.

Despite major advances in the treatment of metastatic colorectal cancer (mCRC), the survival rate remains very poor. This study aims at exploring the prognostic value of RAS ‐mutant allele fraction (MAF) in plasma in mCRC. Forty‐seven plasma samples from 37 RAS ‐mutated patients with nonresectable metastases were tested for RAS in circulating tumor DNA using BEAMing before first‐ and/or second‐line treatment. RAS MAF was correlated with several clinical parameters (number of metastatic sites, hepatic volume, carcinoembryonic antigen, CA19‐9 levels, primary site location, and treatment line) and clinical outcome [progression‐free survival (PFS) and overall survival (OS)]. An independent cohort of 32 patients from the CAPRI‐GOIM trial was assessed for clinical outcome based on plasma baseline MAF. RAS MAF analysis at baseline revealed a significant correlation with longer OS [Hazard ratios (HR) = 3.514; P = 0.00066]. Patients with lower MAF also showed a tendency to longer PFS, although not statistically significant. Multivariate analysis showed RAS MAFs as an independent prognostic factor in both OS (HR = 2.73; P = 0.006) and first‐line PFS (HR = 3.74; P = 0.049). Tumor response to treatment in patients with higher MAF was progression disease ( P = 0.007). Patients with low MAFs at baseline in the CAPRI‐GOIM group also showed better OS [HR = 3.84; 95% confidence intervals (CI) 1.5–9.6; P = 0.004] and better PFS (HR = 2.5; 95% CI: 1.07–5.62; P = 0.033). This minimally invasive test may help in adding an independent factor to better estimate outcomes before initiating treatment. Further prospective studies using MAF as a stratification factor could further validate its utility in clinical practice.