Chemotherapy-induced nausea and vomiting (CINV) remains one of the most impactful toxicities affecting patients' quality of life during cancer treatment. Over decades, randomized trials and other primary studies have built the evidence that informs contemporary antiemetic guidelines. However, the applicability of that evidence to resource-limited settings—where many guideline-recommended regimens may be inaccessible—had not been characterized in detail.
This review aimed to describe the geographic and economic origins of primary research that guideline committees cited as evidence for antiemetic therapy, with the intent of identifying potential inequities in the distribution of seminal CINV studies.
The authors examined the reference lists of three major guideline documents: the 2023 MASCC/ESMO antiemetic guideline, the 2025 NCCN guideline, and the 2020 ASCO guideline. From those reference lists, they identified all cited primary research articles used as evidence for antiemetic therapy. Review articles were explicitly excluded from the analysis.
For each eligible primary study, the review extracted the following items when available: country of origin, World Bank income classification (to determine high-income versus low- and middle-income origin), patient age and sex distribution, primary cancer type, the chemotherapy regimen administered, chemotherapy emetogenicity category, and the antiemetic regimen under study. Findings were synthesized descriptively across the assembled evidence base.
From the combined guideline reference lists, a total of 213 articles were initially identified. Two of these could not be retrieved and one was determined to be a review article, leaving 210 studies eligible for data extraction. When the same patient populations were reported across multiple publications, the reports were consolidated so that each distinct patient cohort was represented once; after consolidation, 195 unique populations remained for analysis.
Among the 195 unique study populations analyzed, the majority of trials enrolled patients receiving highly emetogenic chemotherapy (63.1%). Trials of moderately emetogenic regimens accounted for 27.2% of the evidence base. Studies involving minimally emetogenic chemotherapy made up 8.7%, and those involving low emetogenicity regimens represented 1.0% of included populations.
The review extracted demographic and treatment variables (age, sex distribution, cancer type, chemo regimen, and antiemetic regimen) at the study level, though the abstract does not provide detailed breakdowns of these variables beyond emetogenicity categories.
A central finding was the marked concentration of evidence originating from high-income countries (HICs). Of 191 studies for which an income classification could be determined, 82.7% originated in HICs while only 17.3% came from low- and middle-income countries (LMICs). This imbalance was present across every chemotherapy emetogenicity category, indicating that even for highly emetogenic regimens the primary trial evidence is largely HIC-centered.
The review highlights that because guideline-recommended regimens and lower-cost alternative antiemetic strategies are typically derived from this same evidence base, the limited representation of LMICs could affect external validity and implementation in resource-limited settings.
The evidence supporting contemporary antiemetic guidelines for CINV is concentrated in high-income settings. Given that guideline recommendations are used globally but resource availability varies, the authors recommend that additional research be conducted to evaluate the effectiveness and feasibility of antiemetic regimens in resource-limited contexts. Such studies would help determine whether lower-cost or alternative regimens provide equivalent benefit and are implementable where standard guideline regimens are inaccessible.
The abstract reports key high-level findings but does not provide granular regional breakdowns, detailed demographic distributions, or specific counts of studies by country in the abstract text. Two referenced items were not retrievable and one reference was a review and excluded. The review consolidated duplicate populations, but the abstract does not enumerate which studies were consolidated or give a full account of antiemetic regimens represented; these details would be found in the full article.
Conflict of interest: the authors declare no competing interests.