Iida N, et al. - Researchers examined how gut flora and antibiotics influence the prognosis of patients with liver cancer who have undergone chemotherapy by analyzing two independent clinical studies. To examine the association between use of antibiotics and prognosis, a sub-analysis of a previously reported randomized controlled trial (RCT) on hepatic arterial infusion chemotherapy in patients with hepatocellular carcinoma (HCC) was done retrospectively. In the other study, they performed sequencing 16S ribosomal RNA to prospectively determine the abundance of specific bacterial genus in patients with HCC in addition to examining its association with survival. Patients with HCC who have undergone chemotherapy showed poor prognosis in correlation to using antibiotics targeting anaerobes, whereas there appeared an association of the intestinal anaerobic bacteria, Blautia, with a good prognosis. These findings emphasize the significance of practicing caution regarding overuse of broad-spectrum antibiotics targeting anaerobes in patients with HCC.