A 58-year-old man with newly diagnosed pancreatic cancer presents to the emergency department with acute dyspnea and chest pain. His vital signs show BP 95/60, HR 110, RR 28. D-dimer is markedly elevated at 8.5 μg/mL (normal <0.5). CT pulmonary angiography confirms bilateral pulmonary emboli. His PT is 18 seconds (control 12), aPTT is 52 seconds (control 32), platelet count is 65,000/μL, and fibrinogen is 150 mg/dL (normal 200–400). What is the most likely underlying coagulation disorder?