As NSCLC cases account for 85% of lung cancers, of which approximately third are KRAS mutant lung adenocarcinomas, with 40% tumours harbouring KRAS G12C31, thousands of newly diagnosed KRAS G12C mutant tumour each year would be expected to harbour another concomitant KRAS mutation which could affect patients’ response to G12C inhibitors. The gene discussed is KRAS; the disease is lung carcinoma.