2.7. Cell-Free DNA (cfDNA) Analysis
PD
BLOOD, COLON, DISEASE PROGRESSION
Blood samples were taken at different time points from each patient, and cfDNA was extracted from plasma. For this analysis, only the baseline sample was profiled when patients did not provide any blood samples between the blood collection at baseline and clinical progression. For patients with an ARES overall response (i.e., one evaluation with a PR or SD overall response before PD), three time points were profiled: baseline, responses, and progression. In total, 70 samples from 39 patients had enough DNA to be profiled using the Oncomine Colon cfDNA assay, including a panel of 14 genes. Following sequencing quality control, 55 samples were left from 31 patients, and at least one mutation was detected in 38 samples from 23 patients (see The median PFS of the cohort from the start of regorafenib treatment was 1.84 months. Interestingly, among the 31 patients with adequate cfDNA samples, we observed four patients with a remarkably durable response (PFS ≥ 9 months). When distributed in two groups based on their PFS using nine months as a cutoff (see In our analysis of the six patients with serial sampling, all of whom harbored the same mutation at multiple timepoints, we closely monitored the changes in variant allelic fraction (VAF) throughout the treatment regimen. For each patient, we identified at least one mutation whose VAF diminished concurrently with the clinical response to therapy. Conversely, at the point of disease progression, these mutations exhibited an increase in VAF, as illustrated in 