Association Between Type 2 Diabetes and ECOG Performance Status in Colon and Pancreatic Cancer: Exploring the Role of Systemic Inflammation

Background: Type 2 diabetes mellitus (T2DM) is common in patients with gastrointestinal malignancies, yet its relationship with functional status at cancer diagnosis remains poorly defined. Because both diabetes and cancer are characterized by systemic inflammatory activation, inflammation may be associated with the relationship between diabetes and functional impairment. Methods: We performed a retrospective observational study of 344 patients with colon or pancreatic cancer diagnosed between January 2019 and December 2025, including 172 patients with T2DM and 172 without diabetes, frequency-matched by tumor site. Clinical characteristics, The Eastern Cooperative Oncology Group - ECOG performance status (ECOG-PS) and laboratory parameters were assessed at diagnosis before oncological treatment. Associations between T2DM and ECOG-PS were examined using multinomial and ordinal logistic regression adjusted for age, cancer stage, tumor site, and sex. Multivariable linear regression was used to assess associations with log-transformed C-reactive protein (CRP) and lactate dehydrogenase (LDH). An exploratory analysis evaluated the indirect statistical association through a composite inflammatory score derived from standardized CRP, LDH, and neutrophil count values using 5000 bootstrap samples. Results: T2DM was independently associated with a higher ECOG-PS category in the ordinal model (OR = 1.78; 95% CI 1.14–2.76; p = 0.010). In the multinomial model, T2DM was associated with ECOG 2 versus ECOG 0 (OR = 2.84; 95% CI 1.22–6.63; p = 0.016), whereas the association with ECOG 1 versus ECOG 0 was not statistically significant. After multivariable adjustment, T2DM was associated with 56.4% higher CRP and 34.7% higher LDH levels. A significant indirect statistical association through the composite inflammatory score was observed (β = 0.147; 95% bootstrap CI 0.083–0.216; p < 0.001), whereas the direct association after inclusion of the inflammatory score was not significant (β = 0.020; 95% CI −0.119 to 0.158; p = 0.780). Conclusions: In this selected sample assessed cross-sectionally at cancer diagnosis, T2DM was associated with poorer ECOG performance status and higher systemic inflammatory markers. The observed indirect statistical association through the composite inflammatory score should be interpreted as exploratory because the concurrent assessment of inflammatory markers and ECOG-PS precludes temporal or causal inference. Prospective longitudinal studies are required to clarify these relationships.