Neutrophil-to-lymphocyte Ratio and CA 19.9 as Predictors of Perineural Invasion in Pancreatic Cancer

Pancreatic cancer has an incidence of 1,401,450 new cases diagnosed annually worldwide and is the third leading cause of cancer-related death in Spain. This disease is associated with a poor prognosis, reflected by a 5-year survival rate of less than 5% when all stages are grouped together. Several prognostic factors for pancreatic cancer have been identified. The most relevant include preoperative levels of carbohydrate antigen 19-9 (CA 19.9), surgical margins after resection, venous and/or arterial vascular involvement, and histopathological features such as affected locoregional lymph nodes, or perineural and lymphovascular invasion. Among all these factors, perineural invasion may be the primary independent factor affecting prognosis, particularly in patients with relatively favorable pathological features. The identification of perineural invasion before surgery could influence the clinical management of these patients. It may facilitate risk stratification, allowing the identification of patients who would benefit most from neoadjuvant treatments or more aggressive surgical procedures, such as vascular resections. However, perineural involvement is very difficult to detect preoperatively. Only a few studies have analyzed the possible relationship between CA 19.9 and perineural invasion, and their results are inconsistent. Alternatively, some studies have demonstrated the utility of preoperative multidetector computed tomography in detecting extrapancreatic perineural invasion. However, these radiological tests are still not useful for directly detecting microscopic perineural invasion, especially in early stages. On the other hand, in recent years, evidence has supported that the systemic inflammatory response may play an important role in the prognosis of different malignancies. Among these inflammatory markers, the neutrophil-to-lymphocyte ratio (NLR) has gained prominence. Regarding pancreatic cancer, many studies suggest that elevated preoperative NLR