Tran KT, et al. - Whether proton pump inhibitors (PPIs) and histamine-2 receptor antagonists (H2RAs) impact risk of primary liver cancer was investigated via two large independent study populations. A nested case-control study was conducted within the Primary Care Clinical Informatics Unit (PCCIU) database, in which up to five controls were matched to cases with primary liver cancer. In addition, a prospective cohort study was conducted within the UK Biobank using self-reported medication use and cancer-registry recorded primary liver cancer. Some evidence was found that PPI use was linked to liver cancer, however whether this relationship is causal is still unclear.