A 58-year-old woman with a 10-year history of chronic pancreatitis (alcohol-related) presents with new-onset epigastric pain, anorexia, and weight loss of 5 kg over 1 month. CA 19-9 level is 240 U/mL (normal <37). MRI abdomen shows a 2.5 cm hypointense lesion in the pancreatic body with loss of the fat plane between the lesion and the splenic vessels. The patient has good performance status (ECOG 0) and no distant metastases on staging CT. What is the most appropriate treatment strategy?