KRAS and neoplasm: Our findings are consistent with a study testing tumour growth delay in two genetic variants of a lung adenocarcinoma mouse model after either a single fraction of 11.6 Gy or two fractions of 7.3 Gy in which no significant difference in the response of tumours deficient in p53 (LSL-Kras; p53FL/FL mice) were seen after single or two smaller fractions (p = 0.23), in contrast to tumours with WT p53 (p = 0.002)32.