EGFR 19Del mutations were more frequent in tumours with CTR ranging from 0.25 to 0.5 (71.4%, 5/7) than in those with CTR ranging from 0.5 to 1 (41.2%, 7/17) and from 0 to 0.25 (20.0%, 6/30) (P=0.022) (Table 3). The gene discussed is EGFR; the disease is neoplasm.