Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with conventional treatments having little impact on disease course. Novel approaches are urgently needed to address inherent resistance to the current therapies and to identify new drugs or combinations that will have a high chance of success in pancreatic cancer patients. This proof-of-concept trial is studying the "dynamic" tumor response after the administration of a short course of gemcitabine and nab-paclitaxel (Abraxane) (a) during a window interval (4 weeks= 1 cycle) before surgery in resectable pancreatic cancer (cohort 1 = 21 patients) and (b) during at least 8 weeks (2 cycles) in locally advanced or metastatic pancreatic cancer (cohort 2 = 10 patients).