Berkshire Hathaway shares fell as much as 1.5 percent in after-hours trading in the US after the news that its chief executive, Warren Buffett, is suffering from early prostate cancer.

Buffet, the 81-year-old billionaire investor, said in a letter to shareholders posted on his website, that his condition was "not remotely life-threatening or even debilitating in any meaningful way". He said he would begin a two-month treatment by mid-July which would include daily radiation dosages.

Buffett was diagnosed with stage one prostate cancer.

"I feel great – as if I were in my normal excellent health – and my energy level is 100 percent," said Buffett. He gave no sign that he would step down.

"I will let shareholders know immediately should my health situation change. Eventually, of course, it will. But I believe that day is a long way off," he added.

Stage 1 prostate cancer is common in men and over 241,000 new cases are expected in the US in 2012.

"It means nothing today or tomorrow, stock-wise. It's a shock, but it'll wear off quickly. If the news was he has pancreatic cancer, well, it would be a shock and then a lot of hand-wringing," Jeff Matthews, Berkshire investor and author of the book Secrets in Plain Sight: Business and Investing Secrets of Warren Buffett, told Reuters.

"We all feel bad for Mr Buffett and I wish him nothing but the best in terms of his medical care but I don't know this will have any impact on the equity market," Phil Orlando, chief equity market strategist at Federated Investors, said.

Warren Buffett is the third richest person in the Forbes list of billionaires with a personal wealth of $44 billion (£27 billion).