Washington(CNN) Former GOP presidential nominee Mitt Romney was treated for prostate cancer over the summer, a source close to Romney told CNN Monday.

"He was treated surgically by Dr. Thomas Ahlering at UC Irvine Hospital in California," the source said. "His prognosis is good; he was successfully treated." The source did not provide additional details.

A Romney aide added that the cancer was removed surgically and found not to have spread beyond the prostate.

Romney, the 70-year-old former governor of Massachusetts, is being widely encouraged to run for Utah Sen. Orrin Hatch's seat this year. Hatch announced last week he would retire from the Senate.

Romney spoke to President Donald Trump over the phone Thursday, a White House official confirmed to CNN. Details of their conversation have not been released.