Berkshire Hathaway Inc. (NYSE:BRK/A) CEO Warren Buffett has been diagnosed with stage I prostate cancer, according a letter he released to the company's shareholders Tuesday afternoon.

The condition, however, is "not remotely life-threatening or even debilitating in any meaningful way," said Buffett.

He will have travel restrictions as a part of his two-month daily radiation treatment, which will begin in mid-July. Otherwise, his daily routine won't change, the legendary value investor said.

"I feel great -- as if I were in my normal excellent health -- and my energy level is 100 percent," Buffett said, adding that he discovered the disease as part of a routine cancer screening test. Tests show no indication of the cancer spreading to other parts of his body.

CNN reported that doctors discovered the cancer after Buffett's prostate-specific antigen levels jumped and warranted a biopsy. Buffett received his diagnosis last Wednesday.

Buffett, 81, said his health will "of course" eventually decline, but he believes that day is "a long way off."

In the meantime, he promised to inform shareholders "immediately" should his condition deteriorate.

The debate over who will eventually succeed Buffett as the CEO of Berkshire Hathaway has sparked intense speculation for years. In a 2011 letter to shareholders, Buffett said his successor has been chosen -- as well as two back-up candidates -- although he declined to name those individuals.

Buffett told CNNMoney in December that upon his death, his son, Howard, would follow as chairman of Berkshire Hathaway but wouldn't be involved in strategy or day-to-day decisions.

Jeff Matthews, a Berkshire investor and author of "Secrets In Plain Sight: Business & Investing Secrets of Warren Buffett," told USA Today the news "tells us that he is mortal and also reinforces the idea that the succession planning he has been working on will be needed."

While Buffett will eventually step down someday, investors said he has stitched together a strong group of companies, ranging from railroads to retail that will prosper long after he is gone.

"It's a shock to everybody," said Andy Kilpatrick, author of "Of Permanent Value: The Story of Warren Buffett." "But his life will go on, and Berkshire will go on. There's no need for any emergency alarm. But it's something to watch over the next three to five years."

Shares of Omaha, Neb.-based Berkshire Hathaway fell $1,261, or 1 percent, to $120,048 in midday trading on Wednesday.

The full text of the letter can be seen here.