Survival analysis of patients with PDAC
The ROC curves showed that preoperative serum CA19-9 could predict the prognosis of patients with PDAC (AUC=0.576, 95%CI:0.535-0.615, P=0.003)(Figure 1 ). The optimal cutoff point of preoperative serum CA19-9 to predict survival was 112 U/ml. Then, the patients were categorized into two groups according to the optimal cutoff value of preoperative serum CA19-9: group 1, in which the level of peroperative serum CA19-9 was ≤112 U/ml; and group 2, in which the level of preoperative serum CA19-9 was >112 U/ml.
The results of the univariate and multivariate survival analyses were presented in Table II . In the univariate analysis, the following 8 factors evaluated had a significant effect on survival: age at surgery (<70 years vs ≥70 years), preoperative CA19-9 (≤112 U/ml vs >112 U/ml), preoperative serum CEA (≤5 ng/ml vs >5 ng/ml), postoperative adjuvant chemotherapy, TNM stage, histology grade (low grade vs high grade), perineural invasion and lymphovascular invasion.
PDAC patients with CA19-9 >112U/ml had a significantly less 5-year OS than those with CA19-9 ≤112U/ml (5-year OS: 15.9% vs 22.6%, P<0.001, Figure 2, A ), and patients with high grade also had a significant less 5-year OS than those with low grade (5-year OS: 15.7% vs 23.5%, P<0.001, Figure 2, B ).
In the multivariate analysis, preoperative serum CA19-9 (HR was 1.355 for CA19-9>112 U/ml, P=0.005) and histology grade (HR was 1.545 for high grade, P<0.001) were found to be independent prognostic factors for OS, as were age at surgery (≥70 years), TNM stage and postoperative adjuvant chemotherapy.