Jamie Dimon, whose eight years atop JPMorgan Chase have made him one of Wall Street’s most powerful leaders, said he will start treatment for throat cancer, raising new questions about succession plans at the biggest U.S. bank.Dimon, the chairman and chief executive officer, told employees and shareholders in a memo that his condition is curable and that he will keep running the firm “as normal” during eight weeks of radiation and chemotherapy. The treatment will start soon at Memorial Sloan Kettering Cancer Center in New York, limiting his travel. Dimon, 58, has led JPMorgan since late 2005, navigating the 2008 financial crisis without a loss and doubling annual profit as the lender’s shares climbed about 45 percent. Six months ago, the board credited his ability to resolve government investigations of the bank. The illness will revive questions about how the panel plans to handle succession, said Ralph Cole, a portfolio manager at Ferguson Wellman Capital Management in Portland, Ore.“Transition has always been a question, and now that will be at the top of investors’ minds,” Cole said. “They have to be very vocal about who’s going to be stepping up during the eight-week period. They’ve got to be clear with everybody about who that is.” The bank has deep contingency and succession plans, and Dimon’s illness may serve as no more than a valuable “fire drill,” said Michael Farr, president of Farr, Miller & Washington, a Washington-based asset manager. “The good news is that every indication is that they will never be needed and that Jamie Dimon has many years to work and that he’ll retire on his own schedule as a much older man,” Farr said. “It feels unfair to watch someone who has really been through so much have to suffer through this.” JPMorgan shares (ticker: JPM) fell 60 cents Wednesday to $56.97.In his memo, Dimon said that he feels good, that he’s keeping the board apprised and that he’ll say more if his condition changes. “The prognosis from my doctors is excellent, the cancer was caught quickly and my condition is curable,” Dimon wrote, according to a statement released late Tuesday by the bank. “I have been advised that I will be able to continue to be actively involved in our business, and we will continue to run the company as normal. “The cancer is confined to the original site and the adjacent lymph nodes on the right side of my neck,” he wrote. “Importantly, there is no evidence of cancer elsewhere in my body.” The son of a stockbroker, Dimon is known for his charm and brusque manner. In 2011, he publicly challenged Federal Reserve Chairman Ben Bernanke over new regulations. In 2012, Dimon said the housing market would have bounced back faster with him in charge. “He’s one of the iconic CEOs who’s totally identified with a company,” said Nancy Bush, a bank analyst who founded NAB Research in New Jersey. “It’s tremendously important that people know he’s still there, and I’m sure that will still be happening.” About 27,000 cases of throat cancer are diagnosed annually, with an estimated 6,100 deaths attributed to the disease each year in the U.S., according to the National Cancer Institute. Dimon smoked while working at Commercial Credit Co. in the 1980s before quitting and encouraging fellow executives to do the same, according to the book Last Man Standing: The Ascent of Jamie Dimon and JPMorgan Chase, by Duff McDonald.