Venezuelan President Hugo Chávez's cancer is most likely terminal given the disease's recurrences, and while the president may bounce back for periods, his health is increasingly at risk, say several leading cancer specialists not involved in the treatment.

Mr. Chávez is recovering from surgery in Cuba this week after the president said malignant cells reappeared for a third time in his abdomen. Venezuela's government hasn't disclosed what type of cancer he has or what the surgery was for. But it has described the more than...