Preoperative MRI and CA19-9 for predicting occult lymph node metastasis in small pancreatic ductal adenocarcinoma (≤ 2 cm)

Abstract

Aim: Accurate prediction of occult lymph node metastasis (OLNM) in small pancreatic ductal adenocarcinoma (sPDAC) (≤ 2 cm) is crucial for curative management. This study aims to explore clinical and MRI features associated with OLNM in sPDAC and their pathological and prognostic implications.

Materials and methods: This retrospective study included 135 patients with pathologically confirmed sPDAC who underwent surgery between September 2014 and September 2023. Preoperative multi-sequence MRI, clinical data, and pathological features were analyzed. Univariate and multivariate logistic regression models were used to identify risk predictors of OLNM in sPDAC. Receiver operating characteristic (ROC) analysis was performed to assess diagnostic performance and Kaplan-Meier survival analysis was used to evaluate prognostic outcomes.

Results: OLNM was present in 43 (31.9%) sPDAC patients. Univariate and multivariate analysis identified elevated CA19-9 (> 100 U/mL) (OR = 2.404, P = 0.040) and low apparent diffusion coefficient (ADC) values (OR = 0.243, P = 0.031) as independent predictors of OLNM. The combined clinical-radiological model demonstrated an AUC of 0.740, significantly higher than CA19-9 (AUC = 0.653, P = 0.021) or ADC alone (AUC = 0.635, P = 0.035). sPDAC patients with OLNM exhibited higher rates of lymphovascular invasion (44.2%, P = 0.013) and pathological fat invasion (86.0%, P = 0.030). OLNM was associated with significantly worse OS and DFS (P = 0.034 and 0.043).

Conclusions: OLNM is associated with adverse pathological features and poorer prognosis. The combination of preoperative MRI assessment of ADC and CA19-9 may aid in identifying sPDAC patients at high risk for OLNM.

Clinical trial number: Not applicable.

Keywords: Magnetic resonance imaging; Occult lymph node metastasis; Pancreatic ductal adenocarcinoma.

Fig. 1

The study selection flowchart illustrating patient inclusion and exclusion criteria

Fig. 2

A patient with a 1.3-cm pancreatic ductal adenocarcinoma, baseline CA19-9: 14.7 U/mL, stage pT1N0M0. (a) Pre-contrast T1WI image shows a hypointense mass (red triangle). (b) The T1WI in delayed phase exhibits relative hyperintense. (c) Diffusion-weighted image (b = 500 s/mm²) shows a hyperintense mass (red triangle). (d) The apparent diffusion coefficient (ADC) map exhibits relative hypointensity (mean ADC = 1.726 × 10³ mm²/s; red triangle)

Fig. 3

A patient with a 1.5-cm pancreatic ductal adenocarcinoma, baseline CA19-9 111.6 U/mL, stage pT1N1M0. (a) Pre-contrast T1WI shows a hypointense mass (red triangle). (b) The T1WI in delayed phase exhibits relative hypointense. (c) Diffusion-weighted image (b = 500 s/mm²) shows a hyperintense mass (red triangle). (d) The apparent diffusion coefficient (ADC) map exhibits relative hypointensity (mean ADC = 1.248 × 10³ mm²/s; red triangle)

Fig. 4

ROC curves for predicting occult lymph node metastasis (OLNM) in small PDAC patients for single and combined clinical-radiological parameters

Fig. 5

Kaplan-Meier survival analysis comparing overall survival (OS) and disease-free survival (DFS) between small PDAC patients with occult lymph node metastasis (OLNM) and non-OLNM patients. Small PDAC patients with OLNM demonstrated significantly worse OS (a) and DFS (b) compared to non-OLNM patients (P = 0.034 and 0.043, respectively)