Evaluation of response by FDG-PET/CT and diffusion weighted MRI after radiochemotherapy of pancreatic cancer – a non-randomized, monocentric phase II clinical trial – PaCa-DD-041 (Eudra-CT 2009-011968-11)

Background
Pancreatic cancer is a devastating disease with a five-year survival rate of 20-25%. As approximately only 20% of the patients diagnosed with pancreatic cancer are initially staged as resectable, it is necessary to evaluate new therapeutic approaches. Hence neoadjuvant (radio)chemotherapy is a promising therapeutic option, especially in patients with a borderline resectable tumor. The aim of this non-randomized, monocentric, prospective, phase II clinical study was to assess the prognostic value of functional imaging techniques, i.e., [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography / computed tomography (FDG-PET/CT) and diffusion weighted magnetic resonance imaging (DW-MRI), prior to and during neoadjuvant radiochemotherapy.
Methods
Patients with histologically proven resectable, borderline resectable or irresectable non-metastatic pancreatic adenocarcinoma received induction chemotherapy followed by a neoadjuvant radiochemotherapy. Patients underwent FDG-PET/CT and DW-MRI including T1- and T2-weighted sequences prior to and after neoadjuvant chemotherapy as well as following induction radiochemotherapy. The primary endpoint was the evaluation of the response as quantified by the Standardized Uptake Value (SUV) measured with (FDG-PET). Response to treatment was evaluated by FDG-PET and DW-MRI during and after the neoadjuvant course. Morphologic staging was done using contrast-enhanced CT and contrast enhanced MRI to decide inclusion of patients and resectability after neoadjuvant therapy. In those patients undergoing subsequent surgery, imaging findings were correlated with those of the pathologic resection specimen.
Results
A total of 25 patients were enrolled in the study. The response rate measured by FDG-PET was 85% with a statistically significant decrease of the maximal Standardized Uptake Value (SUVmax) during therapy (p <0.001). Using the mean ADC, response was not detectable with DW-MRI. After neoadjuvant treatment 16 patients underwent surgery. In 12 (48%) patients a tumor resection could be performed. The median overall survival of all patients was 25 months (range: 7 – 38 months).
Conclusion
Based on these limited patient numbers, we could show that this trial design is feasible and that the neoadjuvant therapy regime was well tolerated. To evaluate the response to the combined therapy, FDG-PET/CT may be a reliable method. In contrast, the evaluation of the response using mean the mean ADC, DW-MRI did not show conclusive results.