For a subset of patients it has been shown that a certain type of skin lesion will develop into cancer in 34% of patients if left untreated. There is a drug on the market that currently reduces this event rate to 28%. A pharmaceutical company is developing a new drug to treat these lesions but this would be worthwhile only if the new drug can reduce this further to 23%. In planning for a randomized clinical trial, how many evaluable participants are needed to have 80% power to detect a difference of 28% and 23% in the progression to cancer between the current and new drug?