Systematic review and meta-analysis investigating the efficacy and safety of probiotics in people with cancer

Background/objectives: Probiotics are living microorganisms that confer a health benefit on the host when administered. This systematic review and meta-analysis investigates the efficacy and safety of probiotics in adult and paediatric patients diagnosed with cancer. Methods: A systematic review and meta-analysis was undertaken (PROSPERO registration: CRD42016050252). Randomised controlled trials (RCT), identified through screening multiple databases were included for analysis of efficacy. Non-randomised controlled trials and case reports were included for safety analysis. Outcomes included the reduction in the incidence and severity of diarrhoea, and adverse events. Where possible, data were combined for meta-analysis using a random-effects model. Planned subgroup analyses were not possible through marked heterogeneity of study characteristics. Results: Twenty one studies (N = 2982 participants) were included for assessment of efficacy. Probiotics may reduce the incidence of diarrhoea in patients with cancer [odds ratio (OR) = 0.52, 95% confidence interval (CI) 0.34–0.78, 95% prediction interval (PI) 0.3–0.92, I-sq 36.9%, 5 studies] and the duration of pyrexia [standardised mean difference 0.39 days, 95% CI 0.35–0.43, I-sq 0.01%, 5 studies]. Twenty five studies (N = 2242) were included in the safety analysis. Five case reports showed probiotic-related bacteraemia/fungaemia/positive blood cultures. Definitions and reporting of adverse events were variable and inconsistent. Conclusions: There remain insufficient studies to assess the true effect of probiotics in people with cancer. Meta-analysis suggests probiotics may be beneficial but further studies are still required. Improved reporting of outcomes and adverse events in clinical trials are required to improve accuracy and confidence of conclusions drawn in future updates.