UPDATE 1-US-based stock mutual funds post $6.5 bln outflow, biggest of year -Lipper

NEW YORK, Dec 12 (Reuters) - Investors in U.S.-based funds pulled $6.5 billion out of stock mutual funds in the week ended Wednesday, marking the biggest weekly outflows this year, on worries the U.S. Federal Reserve could scale back its bond purchases as soon as next week, data from Thomson Reuters' Lipper service showed on Thursday.