Review finds chemotherapy nausea research is concentrated in wealthier countries
The analysis found that 82.7% of classifiable studies came from high-income countries, raising questions about how well the evidence fits resource-limited settings.
Moderate evidenceReviewSome caution advised
Medical disclaimer: This article summarizes research findings and is for informational purposes only. It is not medical advice.
Editorial illustration — not from the study.
Researchers examined the studies used to support three major guidelines for preventing and managing nausea and vomiting caused by chemotherapy. They found that most of the evidence came from high-income countries, while relatively few studies came from low- and middle-income countries.
The review also found that most studies involved chemotherapy with a high risk of nausea and vomiting. The findings point to a geographic gap in the research base, but they do not show that any specific anti-nausea medicine or regimen works better or worse in a particular country or health-care system.
The question reviewed
Researchers reviewed the reference lists of the 2023 MASCC/ESMO, 2025 NCCN, and 2020 ASCO guidelines on chemotherapy-induced nausea and vomiting. They identified 213 cited articles, excluded one review, and could not retrieve two articles, leaving 210 studies for data extraction. Reports using the same patient population were combined, producing 195 unique populations for analysis. The researchers recorded each study's country, income classification, participant age and sex, cancer type, chemotherapy regimen and emetogenicity, and antiemetic regimen. The underlying studies involved human patients, but this work itself was a review of previously published research and did not enroll new participants.
What the review concluded
Of 195 unique patient populations, most studies involved highly emetogenic chemotherapy, meaning chemotherapy with a high expected risk of nausea and vomiting: 63.1%. Studies involving moderately emetogenic chemotherapy accounted for 27.2%, minimally emetogenic chemotherapy for 8.7%, and low-emetogenic chemotherapy for 1.0%. Among 191 studies with a known income classification, 82.7% originated in high-income countries and 17.3% in low- and middle-income countries. This pattern continued across all chemotherapy emetogenicity categories. Because the review synthesized findings descriptively, it shows an imbalance in where research was conducted, not a causal effect or a direct comparison of treatment results.
Who this is relevant to
These findings describe where the research supporting anti-nausea guidelines was conducted, rather than showing how well any particular regimen works in a specific patient group. They may be relevant to discussions of evidence and access in different health-care settings, but they do not establish that guideline regimens are effective or ineffective for every resource-limited setting.
What this could mean
Guidelines may be based largely on research from settings with greater access to medicines, staffing, and supportive care than many low- and middle-income countries. This geographic imbalance could make it uncertain how well some guideline-supported approaches reflect the circumstances, available resources, and patient populations in those settings. The review identifies a gap in the research; it does not determine whether current recommendations are appropriate or inappropriate for any particular country or patient group.
Limitations & evidence assessment
The researchers analyzed studies cited by three guidelines, so the results depend on those guidelines' reference lists and may not include every relevant study. Two articles could not be retrieved, and the abstract does not describe how the guideline references were selected or how disagreements in data extraction were handled. The analysis was descriptive and did not measure patient outcomes or compare antiemetic effectiveness between income groups. Country income classification may also not capture differences between individual health-care systems, medicine availability, or patient populations.
Why this evidence level: This was a structured review of studies cited by major antiemetic guidelines and included 195 unique patient populations, which provides a broad picture of the evidence base. However, the analysis was descriptive and focused on study location and characteristics rather than directly comparing treatment effectiveness across settings; the abstract does not provide a formal systematic-review or meta-analysis method.
Evidence levels are editorial estimates derived from study metadata — they are not clinical appraisals.
// Source
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