Olanzapine versus aprepitant based triple antiemetic regimens for the prevention of chemotherapy-induced nausea and vomiting in adult patients receiving highly emetogenic chemotherapy: A systematic review and meta-analysis.

e24088 Background: Chemotherapy-induced nausea and vomiting (CINV) significantly affects treatment tolerance and quality of life. ASCO guidelines recommend a NK-1 receptor antagonist with a 5-HT3 receptor antagonist and corticosteroid for patients receiving highly emetogenic chemotherapy (HEC). Olanzapine has emerged as an alternative antiemetic, with evidence suggesting noninferiority in triple regimens. Given its favorable cost profile, we performed a pooled analysis comparing olanzapine- versus aprepitant-based triple antiemetic regimens for CINV prevention. Methods: This PRISMA-compliant review was prospectively registered in PROSPERO (CRD420261284983). Five databases were systematically searched to identify studies comparing olanzapine (OLZ) versus aprepitant (APR) based triple antiemetic regimens. The primary endpoint was complete response (CR) for prophylaxis of chemotherapy-induced nausea and vomiting (CINV) in adult patients receiving HEC. Statistical analyses were performed in R (version 2025.05.0+496; Posit). Results: 13 studies were included in the final synthesis, comprising 1,557 patients (OLZ: n = 779; APR: n = 788). CR was comparable between groups (RR 1.02, 95% CI 0.95–1.09; I² = 55.8%). Exclusion of Mehta et al. (2017) reduced heterogeneity to zero (I² = 0%). In the acute phase ( < 24 h), CR was also similar between OLZ and APR (RR 1.09, 95% CI 0.98–1.20; I² = 82.7%); however, OLZ demonstrated superior CR in the 10-mg dose subgroup (RR 1.08, 95% CI 1.03–1.14; I² = 74%). For delayed-phase CR (24-120 h), the pooled effect estimate was RR 1.11 (95% CI 0.98–1.27; I² = 84.3%). Control of nausea was significantly improved in the OLZ group compared with APR (RR 1.19, 95% CI 1.01–1.40; I² = 72.8%), particularly in anthracycline–cyclophosphamide–based regimens (RR 1.30, 95% CI 1.09–1.54; I² = 62.9%) and the 10-mg OLZ dose subgroup (RR 1.22, 95% CI 1.01–1.49; I² = 75.2%). Nausea control was also superior in both the acute phase (RR 1.13, 95% CI 1.01–1.27; I² = 76.5%) and the delayed phase (RR 1.31, 95% CI 1.05–1.65; I² = 93.3%). Control of vomiting was comparable between OLZ and APR (RR 0.99, 95% CI 0.92–1.07; I² = 0%), with no significant differences observed in the acute ( < 24 h) phase (RR 1.03, 95% CI 0.97–1.10; I² = 49%) or the delayed (24–120 h) phase (RR 1.00, 95% CI 0.97–1.04; I² = 0%). Conclusions: OLZ-based triple antiemetic regimens provide comparable CR and vomiting control to APR, with superior nausea control, particularly in anthracycline–cyclophosphamide regimens and at the 10-mg dose.