Lung cancers in LSL-Kras; Ink4a/ARFFL/FL mice that received a single fraction of 11.6 Gy had decreased growth compared to unirradiated tumors [factor of 1.53 (SEM – 0.03), n = 26 tumors vs. factor of 2.19 (SEM – 0.03), n = 27 tumors, P = 0.003], but two fractions of 7.3 Gy led to an even better response [factor of 0.88 (SEM – 0.01), n = 14 tumors, P = 0.002, Figure 3A]. This evidence concerns the gene KRAS and lung cancer.