Mitt Romney successfully treated last summer for prostate cancer

— -- Former Massachusetts governor and 2012 GOP presidential candidate Mitt Romney was treated for prostate cancer over the summer, an aide to Romney confirmed to ABC News.

“Governor Romney was diagnosed with slow-growing prostate cancer. The cancer was removed surgically and found not to have spread beyond the prostate,” the aide said.

Romney received treatment at UC Irvine Hospital in California by Dr. Thomas Ahlering, and his prognosis is described as good.

The news of Romney's diagnosis and treatment was first reported by CNN.

Speculation has continued to grow in recent months that Romney, who unsuccessfully ran for president against Barack Obama in 2012, will mount a bid for the U.S. Senate in Utah in 2018 following the announcement that longtime Utah Sen. Orrin Hatch is not seeking re-election.

Romney has not made an official decision on whether he will run for the U.S. Senate in 2018.

An ardent critic of then-candidate Donald Trump in 2016, Romney, who called Trump a “phony” and “a fraud,” was later considered for the role of secretary of state in the Trump administration.

Romney and President Trump spoke last week on the phone and discussed Hatch’s retirement, and the president wished Romney luck in his future endeavors, a source familiar with the call confirmed to ABC News.

ABC News' Katherine Faulders contributed to this report.