Six agencies appear to be in the running for the Commonwealth Bank's most significant advertising pitch in five years.The CBA's chief marketing officer, Andy Lark, announced in early November that the bank's multi-million dollar advertising business was up for review.The pitch marks the end of a four-year relationship with incumbent US agency Goodby Silverstein.Both Goody Silverstein and local agency BMF have been invited to pitch alongside M&C Saatchi, Droga5, DDB and GPY&R.Lark confirmed the identity of the bidders to B&T magazine yesterday. He added that work was underway on creating a short list and has not ruled out taking on two or three agencies at the end of the review process. The review is understood to be due for completion in December.