Various studies observed that metformin is radiosensitising in the case of colorectal and oesophageal cancers by causing G2/M phase arrest, in pancreatic cancer by inhibiting DNA repair, abrogating the G2 phase checkpoint, in oesophageal cancer by activating ATM and AMPK, and in HCC by abrogating the G2/M phase arrest [14]. The gene discussed is ATM; the disease is carcinoma of esophagus.