Olanzapine Versus Aprepitant for the Prevention of Chemotherapy-Induced Nausea and Vomiting: A Systematic Review and Meta-Analysis.

Cancer care faces challenges with chemotherapy-induced nausea and vomiting (CINV). Olanzapine and aprepitant, alone or with traditional antiemetics, promise CINV prevention. Their mechanisms target neurotransmitters, providing better control with manageable side effects. This study aims to rigorously review the efficacy and safety of olanzapine versus aprepitant in preventing CINV.  Randomized clinical trials comparing olanzapine versus aprepitant in preventing CINV were selected following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) 2020 guidelines. A comprehensive literature search was conducted in various databases and registries through March 21, 2024. Quality assessment utilized Cochrane's 'Risk of Bias tool (RoB2)', and Review Manager 5.4.1 synthesized results using a random effect model. The main outcomes focused on odds ratios (ORs) for complete response (CR) in acute, delayed, and overall phases. Safety was assessed from trial descriptions. The certainty of evidence was assessed using GRADE Pro. Two hundred and eighty-two records were identified initially, yielding eight eligible RCTs with a total of 1056 participants after screening. All studies targeted CINV in adults undergoing highly emetogenic chemotherapy. In the acute phase, both drugs demonstrated similar efficacy in nausea and vomiting control (OR = 1.01, 95% CI = 0.63,1.62). During the delayed phase, no significant difference was observed (OR = 0.81, 95% CI = 0.62,1.04). In the overall phase, olanzapine exhibited slightly better nausea control than aprepitant, with statistical significance (OR = 0.76, 95% CI = 0.59,0.99). Emetic control was comparable across treatment arms (OR 0.93, 95 % CI 0.70-1.24). Olanzapine provided a clinically meaningful reduction in nausea. However, the sedation caused by olanzapine, which is significantly higher than that caused by aprepitant, can impair daily functioning, diminish treatment adherence, and increase fall risk.