Pharmacologic prevention of radiotherapy-induced nausea and vomiting: Network meta-analysis including olanzapine-based regimens.

e24087 Background: Radiotherapy-induced nausea and vomiting (RINV) negatively impacts adherence and quality of life. Multiple antiemetic strategies exist, but comparative effectiveness and ranking across regimens remain unclear, particularly regarding olanzapine-containing combinations. Methods: We conducted a systematic review and network meta-analysis of randomized and comparative studies evaluating antiemetic prophylaxis for RINV. Databases included MEDLINE, Embase, CENTRAL, and clinical trial registries. Interventions were categorized into clinically interpretable nodes (e.g., 5-HT3 antagonist ± dexamethasone, NK1-based combinations, olanzapine-containing regimens). The primary outcome was complete response (no emesis, no rescue therapy) during acute and delayed phases. Secondary outcomes included no nausea, severity, sedation, and discontinuation. Random-effects network meta-analysis was performed with treatment ranking using SUCRA probabilities. Results: Twenty-two studies encompassing 3,145 patients were included. Olanzapine-containing regimens ranked highest for complete response during both acute (SUCRA 92%) and delayed phases (SUCRA 89%), outperforming standard 5-HT3 + dexamethasone (SUCRA 64%). NK1-based triple therapy showed intermediate efficacy (SUCRA 78%). Olanzapine regimens had modest increases in sedation (RR 1.14, 95% CI 1.01–1.29) but no significant differences in discontinuation rates. Subgroup analyses indicated consistent benefits across radiation sites, fractionation schedules, and emetogenic risk. Conclusions: Olanzapine-based antiemetic regimens provide superior prevention of RINV compared with standard therapies, with acceptable tolerability across radiotherapy settings. Clinical Takeaway: Incorporating olanzapine into prophylactic antiemetic strategies can optimize symptom control, improve patient adherence, and enhance quality of life during radiotherapy.