The use of GLP-1 receptor agonists, such as glucagon-like peptide- 1 (GLP-1) or exenatide, for the treatment of cancer is described. The GLP-1 receptor agonists are typically delivered using an implanted osmotic delivery device that provides for continuous delivery of the GLP-1 receptor agonist for at least one month. Additional beneficial agents, such as anticancer agents, can also be administered.