Patients with gastric cancer are at high nutritional risk and frequently develop cancer cachexia, a condition associated with systemic inflammation and poorer treatment response and prognosis. Even in the absence of metastatic disease on standard imaging, metabolic and inflammatory alterations may already reflect the interaction between tumor biology and host response.

A 70-year-old female patient was diagnosed on October 11, 2023, with gastric cancer located in the antrum, pathological stage as IV (T3N2M1), ECOG 0. She underwent exclusive surgical treatment with partial gastrectomy on April 16, 2024, at the Hospital de Clínicas of UNICAMP. The PET-CT scan showed FDG uptake in the thickened gastric wall, but without signs of metastases. However, surgery identified metastasis in adipose tissue of the greater curvature/omentum. Preoperative nutritional assessment revealed severe weight loss (18.44% over 6 months), low Body Mass Index (19.9 kg/m²) and a low hand grip strength (10 kg). The patient was classified with severe malnutrition by the Patient-Generated Subjective Global Assessment (PG-SGA). Cachexia was diagnosed according to both Global Leadership Initiative on Malnutrition ‒ GLIM criteria (weight loss, low BMI, low muscle mass, reduced food intake, and systemic inflammation evidenced by a neutrophil-to-lymphocyte ratio [NLR] of 11.5) and Fearon criteria (weight loss, low BMI, low muscularity, and inflammation). Body composition assessment by computed tomography at the level of the third lumbar vertebra demonstrated low muscle mass (Skeletal Muscle Index -SMI of 34.6 cm²/m²). Preoperative plasma analysis using multiplex technology revealed elevated levels of GDF-15 (1825.76 pg/mL), associated with an altered inflammatory and metabolic profile, including IL-6 of 4.51 pg/mL, TNF-a of 2.64 pg/mL, interferon-? of 2.54 pg/mL, and insulin of 265.48. During follow-up, the patient experienced disease progression and died of sepsis, with an overall survival of 9 months. The study was approved by the local Ethics Committee (CAAE:76237023.0.0000.5404).

Although the patient underwent standard imaging procedures during initial staging, no radiological evidence of metastatic disease was identified. However, she already exhibited a preoperative phenotype characterized by systemic inflammation, low skeletal muscle mass, severe malnutrition, and established cachexia, conditions consistently associated with poorer prognosis in gastric cancer. The integration of imaging findings with body composition analysis, inflammatory biomarkers, and comprehensive nutritional assessment tools enabled the early identification of a high-risk clinical and nutritional profile that was not captured by anatomical staging alone. Elevated GDF-15 levels further support its role as a mediator of anorexia, muscle wasting, and adverse clinical outcomes, reinforcing its potential value as a prognostic biomarker.

This case highlights the importance of integrating nutritional status, body composition, and inflammatory and metabolic biomarkers into the initial assessment of patients with gastric cancer. The presence of cancer cachexia may indicate occult metastatic disease, particularly peritoneal carcinomatosis not detected by conventional imaging, allowing earlier identification of patients at higher prognostic risk and supporting more individualized clinical decision-making.