A 62-year-old woman from Mumbai with a 2-month history of epigastric pain, weight loss (5 kg), and new-onset diabetes mellitus is found on contrast-enhanced CT to have a 3.5 cm mass in the pancreatic body with encasement of the superior mesenteric artery (SMA) and splenic vein thrombosis. CA 19-9 is 320 U/mL. There is no evidence of distant metastases. What is the most appropriate next step in management?