RESUMO
AIM: To determinate molecular changes in the downstream epidermal growth factor receptor signaling pathway using serial liquid biopsies in patients with metastatic colorectal tumors (mCRC) under anti-angiogenic treatment. PATIENTS AND METHODS: Determination of RAS mutation in primary tissue samples from colorectal tumors was performed in the 23 patients included in the study at diagnosis using quantitative-polymerase chain reaction. Sequential mutations were studied in circulating tumor (ct) DNA obtained from plasma samples. RESULTS: Twenty-three patients with RAS-mutated primary tumors were included. In the first ctDNA determination, 17 of these patients were found to have wild-type RAS status. Remarkably, three out of these 17 wild-type cases changed to RAS-mutated in subsequent ctDNA assays. CONCLUSION: Serial liquid biopsies in patients with mCRC might be a useful tool for identifying changes in the RAS mutation status in patients who had undergone previous anti-angiogenic therapy. The understanding of these changes might help to better define the landscape of mCRC and be the path to future randomized studies.
