Background: Pancreatic carcinoma is one of the most lethal cancers and is the fourth leading cause of cancer-related death in Japan. Inflammatory responses play decisive roles at different stages of tumor development, including initiation, promotion, malignant conversion, invasion, and metastasis, affecting immune surveillance and response to therapy. We previously reported that pentraxin family members, especially long pentraxin (PTX3), are promising biomarkers for the prognosis of pancreatic carcinoma patients. The objective of the present study was to determine whether PTX3 levels could be a prognostic factor for patients with unresectable or recurrent pancreatic carcinoma. Methods: We analyzed data from two clinical trials (UMIN000002323 and UMIN000009474) using the Kaplan-Meier method and Cox proportional hazards model. We included data from patients who were chemo-naïve pancreatic invasive ductal carcinoma patients, had a 0–2 performance status score, and had adequate organ function. PTX3 levels and other laboratory and clinical data were assessed before initial treatment. Results: Overall, 181 patients with unresectable or recurrent pancreatic carcinoma were evaluated for the baseline plasma PTX3 level (median, mean, and range PTX3: 3.54 ng/mL, 4.34 ng/mL, and 0.9–17.7 ng/mL, respectively). In this study population, the median overall survival was 327 days (95% confidence interval, 281–372 days). The median overall survival was significantly shorter at high PTX3 levels( > 4.34ng/mL) than at low PTX3 levels ( < 4.34ng/mL)(223days vs 409 days; log rank test, P < 0.0001). In a multivariate analysis, the PTX3, C-reaction protein (CRP), and cancer antigen (CA) 19-9 levels, and performance status were independent predictors of survival. High PTX3 levels were associated with high CA19-9 and high CRP levels. Conclusions: We confirmed that a high PTX3 level may be a useful prognostic marker for advanced pancreatic carcinoma. However, the mechanism of tumor inflammation and the exact nature of the role of PTX3 expression remain unclear, calling for investigation of the mechanisms underlying PTX3 activity in carcinoma cells and in the tumor environment. Clinical trial information: UMIN000002323 and UMIN000009474.