BACKGROUNDChemotherapy-induced nausea and vomiting (CINV) commonly affects patient quality of life and the overall effectiveness of chemotherapy. This study aimed to evaluate whether adding neurokinin-1 receptor antagonists (NK1RAs) to 5-hydroxytryptamine-3 receptor antagonists (5-HT3RAs) and corticosteroids provides clinically meaningful benefits in preventing CINV in patients receiving moderately emetogenic chemotherapy (MEC).METHODSWe conducted a systematic review of PubMed, Cochrane Library, and Ichushi-Web to identify clinical studies evaluating NK1RAs combined with 5-HT3RAs and dexamethasone for managing CINV in MEC. The endpoints were complete response (CR), complete control (CC), total control (TC), adverse events, and costs. The data were analyzed using a random effects model.RESULTSFrom 142 articles identified, 15 randomized controlled trials (RCTs), involving 4,405 patients, were included in the meta-analysis. Approximately 60% of the patients received carboplatin (CBDCA)-based chemotherapy. The meta-analysis showed that triplet antiemetic prophylaxis with NK1RA was significantly more effective for achieving CR than doublet prophylaxis in each phase. Regarding CC, the triplet antiemetic prophylaxis was significantly more effective than the doublet in the overall (risk difference [RD]: 0.11, 95% confidence interval [CI]: 0.06-0.17) and delayed (RD: 0.08, 95% CI: 0.02-0.13) phases. For TC, no significant differences were observed in any phase. Adding NK1RA did not cause adverse events.CONCLUSIONSAdding NK1RA to CBDCA-based chemotherapy has shown clinical benefits. However, the clinical benefits of NK1RA-containing regimens for overall MEC have not yet been established and require RCTs that exclusively evaluate MEC regimens other than CBDCA-based chemotherapy.