After Ron Speidel retired, he and his wife, Brenda, ventured around the U.S. in their RV for nine years.

“Then I got the big C,” says Ron, 70. After playing college football as an athletic youth in Cape Girardeau, Missouri, he served as a police officer for 30 years — including 18 as a K-9 handler in high-risk operations.

“I was always very active,” he says, noting his surprise when he discovered blood in his urine during...