Did President Ronald Reagan have colon cancer prior to reelection? Could this be evidence?

In the Gallery of pictures you will find a grouping of pictures of equipment belonging to Captain Glen McKnight MD. He was a doctor for President Ronald Reagan during his Presidency. He was part of a medical team that operated on the President to remove a small polyp from the Presidents colon in May of 1984 and later after President Reagan won reelection found colon cancer in July of 1985. There is a letter from the White House, you will see in the gallery, that thanks the Captain for his ” caring for the President” dated January 1984, some 5 months PRIOR to the removal of the polyp in May of 1984. Captain Glen was Chief of the Radiology Department at the Naval Hospital in Bethesda MD. He was not one of the Presidents regular doctors. We have been unable to find out why President Reagan was being seen by Captain Glen however we do not believe that the White House sends out autographed pictures to every Physician who does routine examinations of the President. Nor do we believe that they would be signed by the Presidents wife under normal circumstances. 11 months after the letter of thanks for “caring for the President”, President Reagan was reelected for his second term. In March of 1985, 4 months later, another endoscopic examination revealed another polyp. In July of 1985 the polyp was removed and another polyp was found. It was then that the news reported that President Reagan was diagnosed with colon cancer. Hmmmm. It does seem as if Captain McKnight traveled with the President for a time as the doctors bag has been inspected by USSS (United States Secret Service) and he owned the shirt with the Presidential Seal for Air Force One. We are wondering what service Captain McKnight provided to the President to warrant an autographed picture and a thank you only months before a diagnosis of cancer was reported in the press? Is there a story here? Maybe something in this lot will provide answers to that question. 

REAGAN CALLED HEALTHY; BENIGN GROWTH IS FOUND. By STEVEN R. WEISMAN, Special to the New York TimesPublished: May 19, 1984.
Participating in the examination of the President today were Dr. Karney; Capt. Glen McKnight, a radiologist; Capt. Ralph Sawyer, an ophthalmologist; Lieut. Comdr. Edward Cattau, a gastrointerologist; Lieut. Comdr. Thomas Hinz, a radiologist; Capt. Kevin O’Connell, a urologist; and Dr. Michael Lemp, an opthalmologist.

http://www.doctorzebra.com/prez/g40.htm
“A (May) 1984 proctoscopic examination disclosed a small polyp in Reagan’s colon. Biopsy showed it was benign. In March 1985, another polyp was found, as were trace amounts of blood in his stool. A change in Reagan’s diet eliminated the blood. He underwent endoscopic removal of the polyp and colonoscopy on July 12, 1985, at Bethesda Naval Medical Center. Colonoscopy disclosed a second, more dangerous tumor — a villous adenoma — that could only be removed by surgery.”

Do any of the below images lead anyone else to believe that President Reagan may have had colon cancer PRIOR to his reelection? 

More images can be found at;  http://estatesales.org/daytona-beach-fl-estate-sales/saturday-october-18th-antiques-457418