Sensitive cell-free DNA assay for accurate detection of RAS and BRAF mutations in liquid biopsies of patients with metastatic colorectal cancer: Final results of the multicentric ColoBEAM study.

The multicentric prospective ColoBEAM study (NCT02751177) aimed to assess the feasibility of using liquid biopsy for the detection of KRAS, NRAS and BRAF gene mutations in patients with metastatic colorectal cancer (mCRC) in a real-world setting. The study involved eight medical centres. Tumour DNA from formalin-fixed paraffin embedded tissue was analysed using either PCR or next-generation sequencing as the gold standard, while circulating tumour DNA from plasma was evaluated using the beads emulsion and magnetics digital PCR technique. Blood sampling was conducted without strict timing constraints, allowing for a real-world reflection of clinical practice. Discrepancies between tissue and blood results were re-evaluated externally to ensure the reliability. A total of 202 patients had KRAS and NRAS (RAS) status available for analysis, and 198 patients had both RAS and BRAF statuses available. Overall, the study confirmed the feasibility of liquid biopsy, achieving a concordance rate of 83.2% for RAS mutations and 82.3% for RAS and BRAF mutations when compared with tissue biopsy. The sensitivity of liquid biopsy for detecting RAS mutations was 77.3%, with a specificity of 94.3%. For RAS and BRAF mutations combined, the sensitivity was 77.0% and the specificity was 93.7%. Further analysis based on patient characteristics at the time of blood sampling showed higher sensitivity in chemotherapy-naive patients (sensitivity, 86.1%; specificity, 91.3%) and in patients with liver metastases (sensitivity, 88.6%; specificity, 89.7%). Sensitivity was also higher when the primary tumour was present (sensitivity, 88.6%) and in cases of disease progression or recurrence (sensitivity, 82.8%). In conclusion, liquid biopsy was a feasible and valuable method for detecting RAS and BRAF mutations in patients with mCRC, offering a less invasive alternative to traditional tissue biopsy in real-world settings. The trial registration number is 2015-A01272-47/NCT02751177 (registered March 3, 2016).