Delayed and long-delayed chemotherapy-induced nausea and vomiting in moderately emetogenic chemotherapy: a scoping review of reporting gaps

BACKGROUND: Chemotherapy-induced nausea and vomiting (CINV) remains a clinically significant adverse event in patients receiving moderately emetogenic chemotherapy (MEC). Although the delayed phase is conventionally defined as 24-120 h after chemotherapy, symptoms may persist beyond this timeframe. However, the extent to which long-delayed CINV (>120 h) has been evaluated in prospective MEC studies remains unclear. PATIENTS AND METHODS: This study aimed to systematically map the definitions and reporting of delayed and long-delayed CINV in prospective MEC trials, with an exploratory quantitative synthesis of reported CR rates across assessment periods. PubMed/Cochrane Library/Medical Online/Ichushi-Web was used to search for studies published between January 2000 and December 2025. Eligible studies reported CR rates and clearly defined delayed-phase outcomes. A meta-analysis of proportions was carried out to estimate the pooled CR rates in the acute, delayed, and long-delayed phases. RESULTS: Twenty-six studies comprising 15 phase III and 11 phase II trials were included. The delayed phase was consistently defined as 24-120 h, with 80.8% of studies restricting outcome assessment to this timeframe. Only a limited number of studies evaluated CINV beyond 120 h. In these studies, the pooled CR rate declined from 71% during the conventional delayed phase to 62% during the long-delayed phase. Exploratory subgroup analyses suggested higher pooled CR rates with neurokinin-1 receptor antagonist-containing regimens and in studies including older patients, whereas lower rates were reported in studies including higher proportions of female patients. CONCLUSIONS: In prospective trials, delayed CINV is almost uniformly evaluated within 120 h. CR rates decline in the long-delayed phase, suggesting that conventional endpoints may overestimate antiemetic efficacy. Extending assessment beyond 120 h may provide a more comprehensive characterization of CINV and should be considered in future prospective trials, particularly for newer agents associated with prolonged emetic risk.