Global inequitable distribution of seminal studies of chemotherapy-induced nausea and vomiting.

BACKGROUND: Chemotherapy-induced nausea and vomiting (CINV) remains one of the most quality of life limiting toxicities of cancer therapy. Decades of trials have produced robust antiemetic evidence, but their applicability to resource-limited settings where guideline-recommended regimens are frequently inaccessible has not been characterized. METHODS: We reviewed the reference lists of the 2023 MASCC/ESMO, 2025 NCCN, and 2020 ASCO antiemetic guidelines to identify all primary research articles cited as evidence for antiemetic therapy. Review articles were excluded. For each study, we extracted country of origin, income classification, age, sex distribution, primary cancer type, chemotherapy regimen, chemotherapy emetogenicity, and antiemetic regimen. Findings were synthesized descriptively. RESULTS: From the reference list, 213 articles were identified. Two could not be retrieved and one was identified as a review, leaving 210 studies for extraction. When the same patient population was reported across multiple studies, the reports were consolidated and represented by the most comprehensive study, resulting in 195 unique populations for analysis. Most studies enrolled patients receiving highly emetogenic chemotherapy (63.1%), followed by moderately emetogenic (27.2%), minimally emetogenic (8.7%), and low emetogenic (1.0%) regimens. The evidence base was overwhelmingly derived from high-income countries (HICs): Of 191 studies with a determinate income classification, 82.7% originated in HICs and only 17.3% in low- and middle-income countries, persisting across every emetogenicity category. CONCLUSIONS: The evidence supporting contemporary CINV guidelines is concentrated in high-income settings. As alternative, lower-cost antiemetic regimens for resource-limited settings are derived from this same evidence base, further studies are needed to assess their effectiveness in these settings.