President Reagan is undergoing his sixth colonoscopy and Nancy Reagan her second mammogram in another round of post-cancer surgery checks against any new tumors.

On their way to their weekend retreat at Camp David, Md., the president and his wife were to stop at the Bethesda Naval Hospital outside Washington for their annual physical examinations and tests to check for any recurrence of cancer.Col. John Hutton, the presidential physician, said Thursday that neither the president nor the first lady has shown any "clinical suggestion of recurrence" of cancer. "Both the president and the first lady have remained completely asymtomatic," Hutton said.

Reagan, who turns 78 in February, had a 2-inch cancerous polyp removed from his colon in July 1985. The 67-year-old first lady had her left breast removed in October 1987 after a cancerous tumor was detected. Hutton said the couple's exams were to begin about 11:15 a.m. MST and conclude about 3 p.m. The couple was expected to travel by helicopter to Camp David afterward.