The Significant PET Signal Changes after Neoadjuvant Treatment for Pancreatic Cancer

Introduction: With the use of effective systemic chemotherapy regimens for pancreatic cancer, many recent studies have been reported improved survival outcomes after surgery. Therefore, it is crucial to evaluate the response after chemotherapy using appropriate diagnostic tests to determine the subsequent treatment method, conversion to surgery or further chemotherapy. In this study, the positron emission tomography (PET) parameters before and after neoadjuvant chemotherapy were compared and factors affecting the survival outcome of the patients were investigated. Method: Among the patients histologically diagnosed with pancreatic ductal adenocarcinoma (PDAC) who underwent therapeutic pancreatectomy from September 2012 to February 2020, received at least 4 cycles of neoadjuvant chemotherapy and took PET images before and after treatment were included. The medical records of 94 patients included in the study were reviewed and the PET parameters, such as max, peak, mean standardized uptake value (SUV), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were calculated and statistically analyzed. Results: At the time of diagnosis, 46 patients (48.9%) were borderline resectable, and 25 patients (26.6%) were locally advanced. 74 patients (78.2%) received FOLFIRINOX regimen preoperatively. The survival outcomes were compared based on TLG value measured after chemotherapy as 55, TLG less than 55 groups showed superior survival results (overall survival: 56 vs. 21 months, p=0.006). This factor was confirmed as hazard ratio 2.450 [95% confidence interval 0.986-6.088] in multivariate analysis (p=0.054). Conclusions: After neoadjuvant chemotherapy in pancreatic cancer patients, PET parameters can be used to predict the prognosis. Further validation through large-scale studies is required.