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.