INTRODUCTION
During
the past decade, immune checkpoint
inhibitors (ICIs) have become a dazzling star in curing multiple
advanced cancers for its breakthrough efficacy and manageable untoward
effect(1, 2). Antibodies inhibiting Cytotoxic T-lymphocyte-associated
antigen-4 (CTLA-4) and programmed death-1/ligand-1 (PD-1/PD- L1) are
mostly and widely researched ICIs in the world(2, 3). Nevertheless, the
gut microbiota has been verified by many researchers to be closely
related to clinical outcome among patients receiving ICIs(4-7).Several
medications that can alter the gut flora distribution are usually
administered to patients along with ICIs thus have adverse or beneficial
impact on the efficacy of ICIs, such as antibiotics (ATBs) use which
have been confirmed to be related to shorter OS and PFS as well as
overall response rates (ORR) compared to ATBs-unexposed cancer patients
undergoing ICIs therapy(8-12).
Except for ATBs,
proton pump inhibitors (PPIs),
maybe one of the most commonly concomitant prescribed medication among
cancer patients(13), can also
significantly decrease the gut microbiota diversity by altering the PH
of gastric acid and delaying gastric emptying(14, 15), thereby, affect
the efficacy of ICIs. Nevertheless,
the effect of PPIs exposure and clinical outcome in cancer patients
undergoing ICIs therapy remains controversial according to current
existing literature. Hence, we
collect the relevant studies and perform a meta-analysis to investigate
the relationship between PPIs exposure and efficacy of ICIs to get a
better understanding of this issue.