A 28-year-old patient has been hospitalized for the pain in the epigastric region. He has a 10-year history of duodenal ulcer (DU). Recently, the pain character has changed: it became permanent, persistent, irradiating to the back. There are general weakness, dizziness, fatigue. The patient has put off weight. Objectively: HR- 68/min, AP- 120/80 mm Hg. What is most likely cause of deterioration?