Clinical benefits of adding olanzapine to 5-HT 3 receptor antagonist, NK 1 receptor antagonist, and dexamethasone for the prevention of nausea and vomiting in highly emetogenic chemotherapy: a systematic review and meta-analysis of the Clinical Practice Guidelines for Antiemesis 2023 from the Japan Society of Clinical Oncology

Olanzapine is an atypical antipsychotic drug used for chemotherapy-induced nausea and vomiting. It is particularly effective in preventing delayed nausea and vomiting induced by highly emetogenic chemotherapy (HEC). However, it has side effects, such as hyperglycemia and somnolence, the efficacy and safety of adding olanzapine to triplet antiemetic therapy (5-HT receptor antagonist, NK receptor antagonist, and dexamethasone) must be verified. We performed a systematic review and meta-analysis to compare the effectiveness of olanzapine combined with triplet antiemetic therapy and triplet antiemetic therapy in preventing nausea and vomiting for HEC. We set five items (hyperglycemia, prevention of vomiting, prevention of nausea, adverse events, and cost (drug costs)) as outcomes and conducted a systematic review. Five randomized controlled trials was extracted and they showed that the addition of olanzapine was effective in control of nausea and vomiting, especially in the delayed phase. Complete response of acute and delayed phase were significantly higher in the olanzapine group. Risk difference was - 0.14 [95% CI - 0.26, - 0.03; p = 0.02] and - 0.14 [95% CI - 0.19, -0.09; p