Athlete who got rectal cancer at 47 had just one symptom

Marcus Wendling toughed out a half Ironman — a grueling triathlon consisting of a 1.2-mile swim, a 56-mile bike ride and a 13.1-mile run — in just under six hours.

He thought the May 2023 race was his greatest physical challenge — until he was diagnosed with Stage 3 rectal cancer months later at the age of 47.

“I eat a healthy diet. I exercise six days a week. I always have been on top of my health,” Wendling, who lives in Dayton, Ohio, told The Post. “So up until that time, you feel like you have this sense of invincibility.”