Introduction
Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal malignancies. According to the World Health Organization, the estimated number of new cases of pancreatic cancer ranked 12th among all malignant tumors in 2020[1]. The 5-year survival rate was approximately 11.5%[2]. Multiple disciplinary therapy based on the tumor stage and biological characteristics of primary lesion is highlighted in improving the survival of patients with PDAC. Therefore, it is vital to classify PDAC more accurately.
The American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) staging system is the most commonly used classification for the prognostic evaluation and treatment decision of PDAC[3]. The TNM classification has undergone continuous improvement to reflect the current understanding of the extent of disease[4]. Several studies have clarified the accuracy of the TNM staging of Pancreatic Cancer (8th ed., 2017) [5,6,7], in contrast, several other studies demonstrated no survival differences between stages of TNM classification and proposed modified TNM or newly staging system[8,9].
Tumor biology shows significant impact on the prognosis of patients with malignancy and has been incorporated into the staging system to improve the accuracy of prognostic prediction[10,11]. Since both tumor burden and malignant degree could reflect the characteristics of tumor biology[12,13], we supposed that combination of the factors which represent tumor burden and malignant degree would provide a full understanding of tumor biology on prognosis of cancer, and incorporating factors associated with tumor biology into staging system could improve the accuracy of the TNM staging system in predicting prognosis. Carbohydrate antigen 19-9 (CA19-9) is associated with the tumor burden [14]and histology grade is associated with the degree of malignancy[15,16]. Therefore, the combination of preoperative serum CA19-9 and histology grade could reflect the tumor biology of PDAC. In the present study, we retrospectively analysed the data of 612 patients with PDAC who underwent curative resections. The aim of this study was to explore the combined effect of preoperative serum CA19-9 and histology grade on the prognosis of patients with PDAC.