What is the difference between a promissory estoppel action and a breach of contract action?

Appellant relies upon the arguments she made in her breach of contract claim, noting that a promissory estoppel action "is identical to a contract action except there is a lack of consideration." Appellant makes no new arguments, other than a single sentence without citation about the relative bargaining strength of the partieswhich we decline to address. (People v. Stanley (1995) 10 Cal.4th 764, 793 [court may treat as waived issue that was not supported by argument or citation to relevant authority].) For the reasons discussed, ante, the trial court did not err in sustaining the demurrer to this cause of action.