Multicenter, Randomized, Double-blind, Placebo-controlled, Phase III Clinical Trial to Investigate the Efficacy and Safety of Dronabinol in the Improvement of ChemOthErapy-induced and Tumor-Related Symptoms in Patients With Locally Advanced or Metastatic Pancreatic Cancer During First-line Chemotherapy (DIsCOvER) - ICH GCP - Clinical Trials Registry