Ryan Decembrino knew something was seriously wrong. When he began experiencing constant abdominal pain five years ago, the 29-year-old in Philadelphia went to the doctor. At that doctor’s insistence, Decembrino underwent a colonoscopy, which found a dozen polyps, but the other doctor who oversaw the scan “wasn’t very concerned because cancer didn’t run in my family,” Decembrino recalls. He was due to come back in three years for a follow-up.

But two years later, the pain got so severe he insisted the doctors take it seriously. A colonoscopy found a tumor in his colon. He went in for surgery and chemotherapy right away. “If I would have waited until my three-year follow-up, I wouldn’t be here today,” he says.