Sen. Tom Coburn, one of Washington’s leading and most fiscally conservative lawmakers, announced Thursday he would be stepping down at the end of the year.

The Republican from Oklahoma had previously announced he would not seek reelection but his latest comments have him leaving Congress two years sooner than he previously planned.

Coburn has been suffering from a recurrence of prostate cancer and hinted about his departure during an interview with reporters last week.

“Serving as Oklahoma’s senator has been, and continues to be, one of the great privileges and blessings of my life," said Coburn, 65. "But after much prayer and consideration, I have decided that I will leave my Senate seat at the end of this Congress."

Known as a conservative maverick during his three terms in the U.S. House in the 1990s, Coburn continued that role after being elected to the Senate in 2004. He is a fierce critic of what he described as excessive government spending, and has vocal about opposing the earmarking of special projects, which was highlighted in his annual “Wastebook” report.

Coburn, a licensed physician who formerly specialized in family medicine, obstetrics and allergy treatment, has been battling prostate cancer, had previously suffered from colon cancer and melanoma. But he said he was stepping down to honor his pledge to serve no more than two terms in the Senate, though he will be stepping down two years before his term expires.

“As a citizen, I am now convinced that I can best serve my own children and grandchildren by shifting my focus elsewhere," Coburn said in his statement. "In the meantime, I look forward to finishing this year strong. I intend to continue our fight for Oklahoma, and will do everything in my power to force the Senate to re-embrace its heritage of debate, deliberation and consensus as we face our many challenges ahead."

Senate Republican Leader Mitch McConnell reacted to the news by describing Coburn as "one of the most intelligent, principled, and decent men in modern Senate history" in a statement.

"Tom is a legend in his own time, an extraordinary man and a deeply serious lawmaker who has made an immense difference to his country and to this body. We will miss him terribly when he leaves the Senate, and we will stand with him every step of the way as he wages this latest of many tough battles that he has fought, and won," the statement read.

The Associated Press contributed to this report.