On this day in 1985, while President Ronald Reagan is undergoing surgery to remove a benign polyp in his large intestine, doctors discover a second polyp and perform a biopsy to determine whether or not it is cancerous.

Reagan’s 1985 surgery was performed at Bethesda Naval Medical Center in Maryland. He was 74 years old at the time and America’s oldest sitting president. Immediately after the procedure, doctors informed the president of the existence of the second, and possibly cancerous, polyp. Reagan and his wife Nancy agreed to schedule a second surgery for its removal the following week.

A clause in the 25th Amendment provides for the transfer of presidential powers to the vice president should the president become temporarily incapacitated (for example while under anesthesia). The decision must be made prior to any procedure. For his 1985 surgeries, Reagan chose not to invoke the clause. By contrast, in 2002, President George W. Bush elected to make the official transfer before he underwent a routine colonoscopy, in light of the fact that he was a wartime president. Therefore, for 20 minutes in 2002, Vice President Dick Cheney was officially in charge of the country, while Bush was undergoing a procedure to remove benign colon polyps.

Reagan’s second polyp did indeed turn out to be cancerous. The following week, doctors removed two feet of the president’s intestine in addition to the diseased polyp. After the surgery, Reagan reportedly quipped, “well, I’m glad that’s all out” and said that he planned to live a long time.

By sharing their experiences, both Reagan and Bush helped to raise the public’s awareness about colon cancer.