The 81-year-old chairman and CEO of Berkshire Hathaway Inc. said in a letter to shareholders that the two-month radiation treatment he and his doctors plan to start in mid-July will restrict his travel but shouldn't otherwise affect his routine.
"I feel great - as if I were in my normal excellent health," Buffett said. "And my energy level is 100 percent. I discovered the cancer because my PSA level (an indicator my doctors had regularly checked for many years) recently jumped beyond its normal elevation and a biopsy seemed warranted."
Buffett said he was diagnosed April 11 and has received tests including a CAT scan, a bone scan and an MRI. He said the tests showed no indication of cancer elsewhere in his body.
Cancer experts say Buffett's diagnosis shouldn't be a major concern because it appears his doctors caught the disease early. Still, the news will remind Berkshire investors of Buffett's mortality.
"The chance of dying of prostate cancer for Mr. Buffett in the next 10 years is probably 2 or 3 percent, so the prognosis is great," said Dr. Ralph deVere White, director of the Comprehensive Cancer Center at the University of California, Davis.
Buffett is known for a no-nonsense approach to investing. He is one of the world's richest men and, in recent years, has become one of its most generous philanthropists.
Buffett's stake in Berkshire Hathaway was worth $44.6 billion as of Tuesday's closing prices before the announcement.
Jeff Matthews, the author of "Secrets in Plain Sight: Business and Investing Secrets of Warren Buffett" and a Berkshire shareholder, said he isn't panicking, and he doesn't think most other shareholders will either.
"I think 99.9 percent of Berkshire's investors will read the press release and take Buffett's statement at face value," Matthews said. "I actually think this doesn't change the picture much at all."
Matthews said anyone who panics and sells Berkshire stock because of this news probably doesn't know the conglomerate and the hands-off way Buffett lets the company's more than 80 subsidiaries operate.
Plus, Buffett and Berkshire's board have a succession plan. Berkshire plans to split Buffett's job into three parts - CEO, chairman and several investment managers - when the company does need to replace him.
Buffett told shareholders in February that Berkshire's board has chosen someone to succeed him as CEO - someday - and he said there are two backup candidates.
None of the three has been publicly identified.
Buffett has said Berkshire hasn't even told the successor and backups who they are. But he has said his son Howard, a member of Berkshire's board, would make an ideal chairman. And Berkshire has hired two hedge fund managers - Todd Combs and Ted Weschler - over the past two years who Buffett says are capable of eventually running the company's entire portfolio.
The AFL-CIO, which owns some Berkshire stock, has submitted a shareholder proposal that's up for a vote at Berkshire's annual meeting in May asking whether the company should be compelled to disclose more specifics about its succession plan. More than 30,000 people typically attend the meeting to hear Buffett and Vice Chairman Charlie Munger answer questions from analysts, reporters and shareholders.
Berkshire's insurance, railroad and utility businesses typically account for more than half of its net income. It also has owns clothing, furniture, brick and jewellery firms and has major investments in such companies as American Express Co., International Business Machines Corp., Washington Post Co. and Wells Fargo & Co.
Although Buffett's investment success has made his a household name - and made him a Wall Street oracle - he still works in his hometown of Omaha and lives in a house he bought in 1958.
Prostate cancer is the most common cancer in men - more than 241,000 new cases are expected to be diagnosed in the United States this year. More than 90 percent are early-stage - like Buffett's - and nearly all men with such diagnoses survive at least five years.
Buffett's case is likely to renew controversy over PSA blood tests. A leading government task force warns against them for men old than 75 because prostate cancer usually grows so slowly in older men that it rarely proves fatal. That means many men are treated and suffer side effects unnecessarily. The American Cancer Society says only men in good health with a life expectancy of at least 10 years should consider a PSA test.
"Mr. Buffett made a decision to get it, but that may not be the right decision for every man in that age group," said Dr. Len Lichtenfeld, the cancer society's deputy chief medical officer.
Likewise for treating the disease. Any man at that age should have "a careful conversation with his physician about the pros and cons of treatment," let alone which type is best, Lichtenfeld said. "We're becoming increasingly aware that not every man needs to be treated."
Buffett has chosen radiation treatment - five days a week for six weeks. During radiation treatment, people feel tired and have some risk of urinary and bowel problems but usually can work and life normally, said Dr. Sean Collins, a radiation oncologist at Georgetown's Lombardi Comprehensive Cancer Center.
"It's kind of like kindergarten - the hardest part is showing up," he said.
Many prostate cancer patients die of something else before the cancer kills them. Buffett concluded his letter with a nod to that fact.
"I will let shareholders know immediately should my health situation change," he wrote. "Eventually, of course, it will; but I believe that day is a long way off."
Berkshire's class B shares rose $1.09 Tuesday to close at $80.76. They fell 95 cents after hours following the announcement of Buffett's diagnosis.