Shanley joins from Help the Aged, where she has been head of individual marketing, wills and legacies for three years.
She was previously head of marketing and communications with the Coin Street Group, the parent company of Coin Street Community Builders, a not-for-profit social enterprise responsible for developing part of London's South Bank.
"The launch of Cancerbackup's What Now? appeal later this year is a great opportunity to build upon the achievements of such an important charity," said Shanley. "The information and service it delivers is second to none, but we want to do more."