Curt Bogard recalls first being more tired than usual during a father and son road trip from Texas to the northeast corner of Maine. When Curt’s wife, Trisha, spoke with him on the phone, she could tell he was not his usual self.

“I told my daughter-in-law that I had to fly home immediately to check on him,” recalls Trisha, who was visiting family in Florida at the time. When she arrived, she noticed Curt’s abdomen was swollen...