Purpose: Malnutrition increases chemotherapy toxicity and impairs quality of life. Previous studies have shown an association between nutrition assessment tools, such as the Geriatric Nutrition Risk Index (GNRI), and adverse events of chemotherapy. However, none are specific to colorectal cancer (CRC). Therefore, we evaluated this association by investigating adverse events needing treatment (AENT) in patients with CRC.Methods: We retrospectively classified 147 patients with CRC into the risk

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... oup (GNRI<98, 85 patients) and the no-risk group (GNRI≥98, 62 patients). We defined AENT as infection requiring antibiotics administration, grade ≥2 leukocytopenia, feasible neutropenia, anemia and thrombocytopenia requiring transfusion, grade≥3 diarrhea, and acute organ failure. Results: We compared the two groups regarding AENT, antibiotic use, admission treatment for AENT, and mortality. Fifty-two (61.2%) and twenty-eight (45.1%) patients in the risk group and no-risk group, respectively, experienced AENT (odds ratio [OR], 0.948; [95% confidence interval, 0.919–0.978]; area under the curve of the receiver-operating characteristic curve, 0.694; [0.608–0.780]). Those in the risk group had increased antibiotic use (OR, 0.945; [0.912–0.979]) and mortality (OR, 0.845; [0.765–0.932]). AENT and performance status were not associated, while GNRI score and chemotherapy toxicity were inversely associated.Conclusion: GNRI can predict a patient's tolerability for cytotoxic chemotherapy. Prospective studies should validate GNRI and nutrition support benefits.