BOGOTA (Reuters) - Colombian President Juan Manuel Santos is healthy and has no cancerous tumors but will take medication and undergo one session of radiotherapy to eliminate any vestiges of a previous bout with the disease, he said on Monday.

Santos, 65, had successful surgery four years ago to remove a tumor in his prostate. He won election in 2010 and is halfway through his second term.

He flew to the United States last week for tests after doctors in Colombia detected elevated levels of prostate-specific antigen (PSA) during a routine check-up.

Men with prostate cancer often have elevated levels of PSA, a protein in the prostate gland.

"This treatment, as the doctors have said, will not at all affect my daily personal or professional activity," the president told reporters outside a clinic in Bogota. "It's good news."

The cancer scare came at a busy time for the Colombian leader, who is trying to push through a revised deal with the Marxist FARC rebel group and get congressional approval for tax reforms.

(Reporting by Julia Symmes Cobb and Luis Jaime Acosta; Editing by Helen Murphy)