EGFR and neoplasm: In these three patients at the time of recurrence, the proportions of EGFR-amplified tumour cells were 18% (0 cycles of adjuvant temozolomide), 20% (6 cycles of adjuvant temozolomide), and 68% (0 cycles of adjuvant temozolomide), indicating that an amplified subpopulation may have been present at a lower clonal frequency initially.