Nutritional Status Assessment Using the Patient-Generated Subjective Global Assessment (PG-SGA) in Individuals with Colorectal Cancer Undergoing Chemotherapy Regimens

<b>Background/Objectives:</b> Colorectal cancer (CRC) has high prevalence and mortality, with a high frequency of malnutrition during chemotherapy (60-70%). Malnutrition reduces treatment tolerance, quality of life, and survival. The Patient-Generated Subjective Global Assessment (PG-SGA) is effective in detecting it, but its use is not systematic. This study aims to analyze the prevalence and degrees of malnutrition in CRC patients undergoing active chemotherapy, using the PG-SGA, and to propose its systematic implementation in oncology care protocols. <b>Methods:</b> Observational, cross-sectional, and descriptive study in patients with stage III-IV CRC receiving FOLFOX, XELOX, or irinotecan regimens. Nutritional status was assessed with PG-SGA and body composition by bioimpedance. <b>Results:</b> The study includes 91 patients. A total of 45.05% of patients required intensive nutritional intervention, 39.56% needed dietary and pharmacological measures, 10.99% required health education, and only 4.4% did not require intervention. FOLFOX was significantly associated with taste alterations (<i>p</i> < 0.001), nausea (<i>p</i> = 0.020), unpleasant odors, and eating problems; XELOX with diarrhea (<i>p</i> = 0.009) and xerostomia (<i>p</i> = 0.038). Irinotecan was related to poorer functional capacity (<i>p</i> = 0.042). Oxaliplatin was linked to loss of appetite (<i>p</i> = 0.034) and unpleasant odors (<i>p</i> = 0.035). Older age correlated with a greater need for intensive interventions. <b>Conclusions:</b> The study shows a high nutritional risk in oncology patients, particularly in those with colorectal cancer undergoing FOLFOX treatment, associated with symptoms that impair intake and functional capacity. The systematic implementation of nutritional screening from the onset of treatment, using tools such as the PG-SGA and GLIM criteria, is essential for early detection and individualized management, improving therapy tolerance, clinical outcomes, and quality of life.