Concomitant medication reporting should accompany fecal microbiota transplantation plus anti-PD-1 therapy in gastric cancer

This commentary discusses the phase I study of fecal microbiota transplantation plus anti-programmed cell death protein 1 therapy in refractory microsatellite-stable gastric cancer. We suggest that this strategy should be treated as a pharmacomicrobiomic intervention rather than only as an immunotherapy combination. Evidence from fecal microbiota transplantation trials and microbiome immunotherapy studies indicates that antibiotics, proton pump inhibitors, corticosteroids and other microbiome-modifying exposures may affect donor strain engraftment, immune activation, response assessment and safety. In China and other Asian settings, where acid suppression, Helicobacter pylori history, perioperative antibiotic use and nutritional interventions are common, standardized concomitant medication reporting would make future studies more interpretable and transferable.