ATM and colorectal cancer: When comparing the mutation frequencies of selected genes (BRAF, KRAS, TP53, APC, PIK3CA, CTNNB1, ATM, PTEN and BRCA1) that are commonly known for colorectal cancer 15 (Fig. 1A), TP53 (left = 80%, right = 55.3%; p = 0.002) and APC (left = 77.6%, right = 57.5%; p = 0.013) showed significant difference between left-sided and right-sided tumors with higher mutation frequencies on the left-sided tumors.