* Class B shares down 67 cents in early trade
* Investors say Berkshire may be buying stock
April 18 (Reuters) - Shares in Berkshire Hathaway Inc fell less than 1 percent in early trading on Wednesday, a relatively limited reaction to the news that Chief Executive Warren Buffett has stage 1 prostate cancer and will start radiation treatment this summer.
Buffett said Tuesday that he had the early-stage illness and that his condition "is not remotely life-threatening or even debilitating in any meaningful way."
A number of long-term Berkshire shareholders shrugged off the news, given Buffett's good prognosis and the succession planning Berkshire had already started.
"We've owned the stock nearly continuously for 13 years. We've thought about succession a lot," said David Rolfe, chief investment officer of Wedgewood Partners, which holds Berkshire Class B shares.
"Somebody needs to say to themselves before they dump their Berkshire, in the mid-$70s ... there's a chance they could be selling their shares back to Buffett," Rolfe added, referring to a buyback Berkshire launched late last year.
Class A shares fell $1,110 to $120,200, while the more widely held Class B shares fell 67 cents, or 0.8 percent, to $80.09.
After underperforming the S&P 500 in 2011, the stock has lagged again this year, with the Class B shares making just half the gains of the broader market through Tuesday. (Reporting By Ben Berkowitz; editing by John Wallace)