Probiotics for the prevention or treatment of chemotherapy- or radiotherapy-related diarrhoea in people with cancer.

Systematic review and meta-analysis of randomized trials in adults with cancer receiving chemotherapy, radiotherapy, or both, evaluating probiotics for prevention or treatment of therapy-related diarrhoea. The included studies were conducted across multiple countries and cancer settings, especially pelvic radiotherapy and some chemotherapy regimens.

Oral probiotics were tested in varied formulations across the included trials, including single-strain and multi-strain products, probiotic capsules, sachets, and fermented milk or yogurt preparations. Dosing ranged from 1 sachet three times daily to 2 capsules twice daily or 96 mL three times daily, with treatment started 1 day before chemotherapy, 7 days before radiotherapy, or during chemoradiation and continued from days to 24 weeks, depending on the trial.

Probiotics may reduce chemotherapy- or radiotherapy-related diarrhoea in some settings, but the evidence was limited, heterogeneous, and low or very low certainty. Several trials reported fewer diarrhoea events with probiotics, for example 42/243 versus 119/239 and grade 3/4 diarrhoea 8/243 versus 69/239 in one large study, and 3/32 versus 14/31 grade 2/3 diarrhoea in another. Other trials found no clear benefit, such as diarrhoea in 69/81 versus 80/86 (RR 0.92; 95% CI 0.82 to 1.02) or grade 2 or higher diarrhoea in 51/81 versus 34/43 (RR 0.75; 95% CI 0.55 to 1.03). No serious adverse events or deaths were attributed to probiotics, although some studies reported more bloating.

The evidence base was underpowered and clinically heterogeneous, with different probiotic strains, doses, formulations, cancer treatments, and outcome definitions. Certainty was low to very low, some outcomes were inconsistently reported, and several analyses were based on small trials, limiting confidence and generalizability.