A single blood sample (20mL) will be collected after the patient has given informed consent. The blood sample will be collected within 4 weeks prior to the patient starting chemotherapy. Blood samples collected will be processed in accordance with the Guardant360 Clinical Blood Collection Kit instructions (Guardant Health, Inc.).~Patient outcomes with respect to response rate, progression-free survival, overall survival, toxicities and other co-morbid conditions will be ascertained by medical record review conducted by the study personnel. Prospective clinical data that will be collected include: patient demographics, tumor stage and pathological tumor characteristics at diagnosis, laboratory data at diagnosis and serial pre-specified time points, imaging outcomes, chemotherapy information, date of recurrence, and date and cause of death.~Although the data will be censored at the study end-points, the patient's medical record will be reviewed indefinitely to follow the health outcomes.
The study aims to explore the clinical utility of circulating tumour DNA (ctDNA) in assessing for alterations of anti-epidermal growth factor receptor (EGFR) primary resistance in RAS and BRAF wild-type metastatic colorectal cancer (CRC) patients treated with anti-EGFR monoclonal antibodies (cetuximab / panitumumab) in combination with fluorouracil (FU)-doublet chemotherapy.